Distressed asset mostly hidden by firm (8)
I believe the answer is:
harassed
'distressed' is the definition.
(thesaurus)
'asset mostly hidden by firm' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'hidden by' means one lot of letters goes inside another (inserted letters are hidden inside).
'firm' becomes 'hard' (both can mean durable or strong).
'asset' with its final letter removed is 'asse'.
'asse' placed inside 'hard' is 'HARASSED'.
(Other definitions for harassed that I've seen before include "Distraught" , "Pestered; under strain" , "Constantly tormented" , "Constantly intimidated" , "Plagued" .)