Waterproof clothing waterproofs family (8)
I believe the answer is:
sealskin
'waterproof clothing' is the definition.
'sealskin' can be an answer for 'clothing' (sealskin is a kind of clothing). I'm unsure of the 'waterproof' bit.
'waterproofs family' is the wordplay.
'waterproofs' becomes 'seals' (I've seen this in another clue).
'family' becomes 'kin' (synonyms).
'seals'+'kin'='SEALSKIN'
Can you help me to learn more?
(Other definitions for sealskin that I've seen before include "Marine fur" , "Fur from the sea" , "prepared fur" , "Fur - lean kiss (anag)" , "Form of fur for garments" .)