Rough bit of fun, eventually... (6)
I believe the answer is:
uneven
'rough' is the definition.
(associated in meaning)
'bit of fun eventually' is the wordplay.
'bit of' says the answer is hidden in the clue.
'UNEVEN' can be found hidden inside 'fun eventually'.
(Other definitions for uneven that I've seen before include "Bumpy - odd" , "Inconsistent in quality or shape" , "Patchy" , "Not uniform or smooth" , "Not smooth or flat" .)