Forceful surgeon engaging macho types (8)
I believe the answer is:
vehement
'forceful' is the definition.
(I've seen this before)
'surgeon engaging macho types' is the wordplay.
'surgeon' becomes 'vet' (I've seen this in other clues).
'engaging' means one lot of letters goes inside another.
'macho types' becomes 'hemen' (a he-man is a muscular man).
'vet' going around 'hemen' is 'VEHEMENT'.
(Other definitions for vehement that I've seen before include "Forceful and with full conviction" , "Vigorous, emphatic" , "Vet he-men showing strong feeling" , "Emphatic, intense" , "Forcible" .)