Adding warmth to connection lacking heart (6)
I believe the answer is:
lining
'heart' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'adding warmth to connection lacking' is the wordplay.
'adding warmth' becomes 'ing' (I can't explain this - if you can you should give a lot more credence to this answer).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'connection' becomes 'line' (line is a kind of connection).
'lacking' means to remove the last letter (the word is incomplete or lacking).
'line' with its final letter taken off is 'lin'.
'ing' put after 'lin' is 'LINING'.
Can you help me to learn more?
(Other definitions for lining that I've seen before include "Extra layer inside another" , "Inner piece of material" , "Layer on the inner surface" , "Backing for curtain, garment etc" , "See 21" .)