What keeps out water from paintings by family members (7)
I believe the answer is:
oilskin
'what keeps out water' is the definition.
(waterproof material)
'paintings by family members' is the wordplay.
'paintings' becomes 'oils' (oil paintings).
'by' is a charade indicator (letters next to each other).
'family members' becomes 'kin' (kin means one's relations).
'oils'+'kin'='OILSKIN'
'from' acts as a link.
(Other definitions for oilskin that I've seen before include "security for a rainy day" , "Waterproof fabric" , "protective cloth" , "Heavy-duty waterproof" , "material" .)