Clothing is hot, to some extent (5)
I believe the answer is:
habit
'clothing' is the definition.
(I know that clothing can be written as habit)
'hot to some extent' is the wordplay.
'hot' becomes 'h' (abbreviation eg on taps).
'to some extent' becomes 'a bit' (to a small extent).
'h'+'abit'='HABIT'
'is' is the link.
(Other definitions for habit that I've seen before include "Custom or established practice" , "Dress - custom - practice" , "Monk's gown or custom" , "nun gets into" , "Custom or monk's robe" .)