Hermit's expert article on living? (10)
I believe the answer is:
crustacean
'hermit's' is the definition.
(hermit crab is an example)
'expert article on living?' is the wordplay.
'expert' becomes 'ace' (ace is a kind of expert).
'article' becomes 'an' (indefinite article).
'on' is a charade indicator (letters next to each other).
'living?' becomes 'crust' (to earn a crust is to earn a living).
'ace'+'an'='acean'
'acean' put after 'crust' is 'CRUSTACEAN'.
(Other definitions for crustacean that I've seen before include "Such as a barnacle" , "Creature like a shrimp or lobster" , "crab, for example?" , "Hard-shelled animal" , "Perhaps crab" .)