Little-known old boy's meeting French priest (7)
I believe the answer is:
obscure
'little-known' is the definition.
(I've seen this before)
'old boy's meeting french priest' is the wordplay.
'old boy's' becomes 'OBs' (abbreviation for a private school 'old boy').
'meeting' says to put letters next to each other.
'french priest' becomes 'cure' (French for 'priest').
'obs'+'cure'='OBSCURE'
(Other definitions for obscure that I've seen before include "Indistinct or not well-known" , "Dark - secret - inconspicuous" , "Enigmatic (like Jude?)" , "Insignificant" , "Overshadow or eclipse" .)