Priest caught in trap by a French heavenly body (7)
I believe the answer is:
neptune
'heavenly body' is the definition.
(Neptune is an example)
'priest caught in trap by a french' is the wordplay.
'priest' becomes 'p' (ecclesiastical abbreviation).
'caught in' means one lot of letters goes inside another.
'trap' becomes 'net' (net is a kind of trap**).
'by' says to put letters next to each other.
'a french' becomes 'une' ('a' in French).
'p' put into 'net' is 'nept'.
'nept'+'une'='NEPTUNE'
(Other definitions for neptune that I've seen before include "King of the sea" , "Poseidon" , "musical work" , "Roman god of the sea, with trident" , "Sea god - outer planet" .)