Inquisitor 1622

[Ripper]

I'm stuck!!
I'm having 'trouble' with the four corners. I realise this has something to do with no crossword title/preamble (or that's what I think!)
1 across: Gazelle: facial feature recalled spirit (5) ?H?R? Mhorr? but why and if it is it gives me RR?N for 4 down: River to flow beneath historic Argo (4) well wordplay gives RRUN ??????
Any help desperately needed!!
Thanks in advance

[ProfessorMaisie]

1a Is thematic (3 letters removed) full answer CHINKARA (ARAK is the 'recalled spirit).
4d ARUN

[ProfessorMaisie]

...there's a letter missing from the clue to 4d - the chemical symbol for Argo(n) was A in the past.

[Ripper]

Thank you ProfessorMaisie, thanks to you I think I might have an idea what to do!
Is 'what is missing' in the title/preamble (i.e. what makes it) the item missing from some clues? If you see what I mean! And the missing letters from some clues spell this item? Which is also 21 across?
Lots of ???'s
Thanks for your help.

[Nical]

Just in case PM isn't around - yes, yes, yes, Ripper.

[Ripper]

Thank you both - up to the pub now to celebrate!

[Nical]

I only confirmed your thoughts, Ripper - but glad you're finished.