Brute's in form -- on steroids! (7)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
monster
'brute's' is the definition.
(thesaurus)
'in form on steroids' is the wordplay.
'in' indicates a hidden word.
'MONSTER' can be found hidden inside 'form on steroids'.
(Other definitions for monster that I've seen before include "Large, ugly and frightening imaginary creature" , "A dragon" , "Vile creature" , "Fabulous beast" , "Huge - beast" .)