Should be a bit of a rough time (5)
I believe the answer is:
ought
'should be' is the definition.
(I've seen this before)
'a bit of a rough time' is the wordplay.
'a bit of' indicates a hidden word (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'OUGHT' can be found hidden inside 'rough time'.
(Other definitions for ought that I've seen before include "Verb implying duty; zero, nothing (archaic)" , "Tough (anag)" , "Be logically necessary" , "Anything at all (archaic)" , "Strange thing" .)