Where you need a warm cover handy? (5)
I believe the answer is:
rugby
'where you need a warm' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'cover handy?' is the wordplay.
'cover' becomes 'rug' (rug is a kind of cover).
'handy?' becomes 'by' (I can't justify this - if you can you should give a lot more credence to this answer).
'rug'+'by'='RUGBY'
Can you help me to learn more?
(Other definitions for rugby that I've seen before include "Public school founded in 1567" , "Sport with oval ball" , "Type of football; school" , "Game named after school" , "Town in Warwickshire" .)