Jack's last in York church body (5)
I believe the answer is:
knave
'jack's' is the definition.
(synonyms)
'last in york church body' is the wordplay.
'last in' says to take the final letters.
'church body' becomes 'nave' (I've seen this in other clues).
The last letter of 'york' is 'k'.
'k'+'nave'='KNAVE'
(Other definitions for knave that I've seen before include "Villain - jack" , "one found amongst thieves" , "cheat of old" , "Varlet; Jack" , "sinner?" .)