Passionate animal doctor accepting macho types (8)
I believe the answer is:
vehement
'passionate' is the definition.
(thesaurus)
'animal doctor accepting macho types' is the wordplay.
'animal doctor' becomes 'vet' (I've seen this before).
'accepting' means one lot of letters goes inside another.
'macho types' becomes 'hemen'.
'vet' placed around 'hemen' is 'VEHEMENT'.
(Other definitions for vehement that I've seen before include "Zealously forceful" , "Showing strong feeling, impassioned" , "Showing strong feeling, like even them" , "Fervid" , "Passionate, intense" .)