Exposed unctuous favourites and hangers-on (7)
I believe the answer is:
limpets
'hangers-on' is the definition.
Although both the answer and definition are plural nouns, I don't understand how they can define each other.
'exposed unctuous favourites' is the wordplay.
I cannot really understand how this works, but
'favourites' could be 'pets' ('pet' can be a synonym of 'favourite') and 'pets' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for limpets that I've seen before include "Marine molluscs that cling tightly to rocks" , "Proverbially clingy marine gastropods" , "'Molluscs, they cling to rocks (7)'" .)