Writer joins church for money (5)
I believe the answer is:
pence
'for money' is the definition.
(I've seen this before)
'writer joins church' is the wordplay.
'writer' becomes 'pen' (something which writes).
'joins' says to put letters next to each other.
'church' becomes 'ce' (Church of England).
'pen'+'ce'='PENCE'
(Other definitions for pence that I've seen before include "some European capital" , "Small coppers" , "Fractions of a pound" , "Lowest denomination of British currency" , "p" .)