Religious faction determined to recruit 100 (4)
I believe the answer is:
sect
'religious faction' is the definition.
(I've seen this before)
'determined to recruit 100' is the wordplay.
'determined' becomes 'set' ('set' can be a synonym of 'determined').
'to recruit' is an insertion indicator (in the sense of bringing in).
'100' becomes 'c' (roman numeral).
'set' going around 'c' is 'SECT'.
(Other definitions for sect that I've seen before include "Dissenting body" , "Denomination" , "Subdivision of a larger religious group" , "Dissenting clique of a religion" , "Group of people with unusual religious beliefs" .)