18 'exalt' = two words (4+2 letters) then minus the Y from the next 4 letter word, and the A from the last word.
18d 6 letter word for 'hang around' but minus 'O(ne's) first' = a US measure.
25d the first 3 letter word is the usual for a marine creature (2x A dropped).
Thank you PM & N. Managed to muddle through 25d with a no of groans and you have confirmed the first two words I have for 18a but the final two words are not fitting, the two suggestions I am trying to fit in are either 5 & 4 which would allow the Y or 3 & 6 which wouldn't, whatever I try makes a gobble-de-gook of the RH name, another nudge please.
Forgive the late reply, thank you N that is the word I had in mind but cannot see the connection to losing a L or Chicago, nor can I get my head around 28a. Have the book & author, indeed it was quite a cult book when published, can't say I really enjoyed it.