Go after religious adherent in speech (4)
I believe the answer is:
seek
'go after' is the definition.
(thesaurus)
'religious adherent in speech' is the wordplay.
'religious adherent' becomes 'sikh' (I've seen this before).
'in speech' indicates a 'sounds like' (homophone) clue.
'sikh' sounds like 'SEEK'.
(Other definitions for seek that I've seen before include "Try to locate or reach" , "'. . . . and ye shall find'" , "Go looking for" , "Try to find" , "Hunt, look for" .)