Opposing social worker going to India (4)
I believe the answer is:
anti
'opposing' is the definition.
(prefix meaning 'opposing')
'social worker going to india' is the wordplay.
'social worker' becomes 'ant' (ants are social insects).
'going to' says to put letters next to each other.
'india' becomes 'i' (phonetic alphabet: alpha, bravo, charlie etc.).
'ant'+'i'='ANTI'
(Other definitions for anti that I've seen before include "Who pooh-poohs all" , "Opposed to followers of Hitler" , "Prefix meaniing against" , "(Person who is) not in favour" , "Negative vote" .)