Try to find someone faithful using phone (4)
I believe the answer is:
seek
'try to find' is the definition.
(I've seen this before)
'someone faithful using phone' is the wordplay.
'someone faithful' becomes 'sikh' (member of the Sikh faith).
'using phone' indicates a 'sounds like' (homophone) clue (how it might sound on the phone).
'sikh' sounds like 'SEEK'.
(Other definitions for seek that I've seen before include "Try to find" , "Attempt - search" , "Hunt, look for" , "Try to locate or reach" , "'. . . . and ye shall find'" .)