Troublesome pants could fit if nothing's removed (9)
I believe the answer is:
difficult
'troublesome' is the definition.
(similar in meaning)
'pants could fit if nothing's removed' is the wordplay.
'pants' indicates an anagram (UK informal term for 'nonsense' or 'rubbish').
'nothing' becomes 'O' (looks like zero - 0).
'removed' suggests deleting specific letters.
'could'+'fit'+'if'='couldfitif'
'couldfitif' with 'o' removed is 'culdfitif'.
'culdfitif' with letters rearranged gives 'DIFFICULT'.
(Other definitions for difficult that I've seen before include "Demanding" , "Requiring much effort" , "Challenging" , "Hard, not easy" , "Trying" .)