Turn of phrase used in papers on the Isle of Man (5)
I believe the answer is:
idiom
'turn of phrase' is the definition.
'papers on the isle of man' is the wordplay.
'papers' becomes 'id' (identification papers).
'on' is a charade indicator (letters next to each other).
'the isle of man' becomes 'iom'.
'id'+'iom'='IDIOM'
'used in' acts as a link.
(Other definitions for idiom that I've seen before include "Eg, over the moon" , "Special turn of phrase" , "Distinctive speech" , "Manner of speaking or writing" , "Peculiarity of phrase in a language" .)