Forceful, keeping macho types in check (8)
I believe the answer is:
vehement
'forceful' is the definition.
(I've seen this before)
'macho types in check' is the wordplay.
'macho types' becomes 'hemen' (a he-man is a muscular man).
'in' means one lot of letters goes inside another.
'check' becomes 'vet' (I've seen this before).
'hemen' put within 'vet' is 'VEHEMENT'.
'keeping' is the link.
(Other definitions for vehement that I've seen before include "Zealously forceful" , "Passionate, intense" , "Ardently forceful" , "Forceful, emphatic" , "Fervid" .)