All steroids in sport? Incompatible (3,8)
I believe the answer is:
ill-assorted
'incompatible' is the definition.
'all steroids in sport?' is the wordplay.
'in sport?' is an anagram indicator ('in sport' can mean 'playfully').
'all'+'steroids'='allsteroids'
'allsteroids' is an anagram of 'ILL-ASSORTED'.
(Other definitions for ill-assorted that I've seen before include "Unsuitably matched" , "Not matching" .)