Unite in providing something warm (4)
I believe the answer is:
knit
'unite' is the definition.
(I've seen this in another clue)
'providing something warm' is the wordplay.
I cannot quite understand how this works, but
'something' could be 'it' (I've seen this in other clues) and 'it' is present in the answer.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for knit that I've seen before include "Unite together" , "Make a scarf, say" , "Interweave" , "manufacture clothing?" , "Put together" .)