Insular Spaniard working as cathedral junior (5,5)
I believe the answer is:
minor canon
'cathedral junior' is the definition.
'insular spaniard working' is the wordplay.
'insular spaniard' becomes 'minorcan' (someone from Minorca, an island of Spain).
'working' becomes 'on'.
'minorcan'+'on'='MINOR CANON'
'as' is the link.
(Other definitions for minor canon that I've seen before include "assistant minister" , "clergyman" .)