Times Jumbo 989

[MCC]

I've got the answers for these (I think!) but can't follow the wordplay.
13 across - Small group not one involved in a large-scale fiddle (5) - C?L?O - assume it must be cello - large-scale fiddle - and can follow small group=cell, but 'not one' = 'o'? That's like Baldrick's defintion of 'cat' - 'not a dog'!
20 across - International organisation's worry gets you down (6) - U?S?AT - assume it must be unseat, made up of uns=international organisation's and eat=worry, but 'gets you down' = 'unseat'? How?
34 down - Correct orientation ultimately needed in the sea off Lebanon (5) - E?E?D - must be emend=correct, and I assume the sea off Lebanon is 'med' with 'n'=orientation ultimately in it, but where does the other 'e' come from?
55 across - So as to drag drunk outside, lobby's emptied (9) - T?D?O?S?Y. Must be 'tediously' - connection with 'drag', and i can see 'ly' for 'Lobby's emptied' but the rest has me mystified.
56 across - Goal to stop criminal following general expression of exasperation (6,7) G?R?O B?N?E?T Must be GORDON BENNETT, but, other than the connection between don and criminal and net stopping goal, I'm baffled by this one, too.
Help, please?

[bibblebub]

13a) yes
20a) refers to getting off a horse
34d) lebanon's at the eastern end of the med thus e med
55a) 'drunk' implies anagram of 'outside'
56a) goal = NET, criminal = BENT, general = GORDON => GORDON BENnetT

[HowardKennitby]

Re CELLO - possibly 'not one' = nobody = 0

[MCC]

Thanks, bibblebub, andHK. I put my hands up to the last three - really embarrassed at missing the anagram pointer in 55a - but I still plead the 'Baldrick' defence in 13a and surely there's a tense confusion in 20a? There were some really good clues in this one, but some were much too contrived. Many thanks for your help, though.