Winter feed receptacle ... a big thing (7)
I believe the answer is:
whopper
'big thing' is the definition.
'whopper' can be an answer for 'thing' (whopper is a kind of thing). I am unsure of the 'big' bit.
'winter feed receptacle a' is the wordplay.
'winter feed receptacle' becomes 'whop' (I can't explain this - if you can you should believe this answer much more).
'a' becomes 'per' (eg 'one a day' means 'one per day').
'whop'+'per'='WHOPPER'
Can you help me to learn more?
(Other definitions for whopper that I've seen before include "Enormous lie" , "A big one, lie or fish" , "Giant pork pie?" , "Huge one; lie" , "as related by angler?" .)