She introduced warmth with a cover (7)
I believe the answer is:
sheathe
'cover' is the definition.
(to sheathe something is to cover it)
'she introduced warmth with a' is the wordplay.
'introduced warmth' becomes 'the' (I can't explain this - if you can you should believe this answer much more).
'with' says to put letters next to each other.
'the' put after 'a' is 'athe'.
'she'+'athe'='SHEATHE'
Can you help me to learn more?
(Other definitions for sheathe that I've seen before include "Put into scabbard" , "Put (a sword) it its cover" , "Put (a sword) into its holder" , "Put (a sword) into case" , "Cover in case" .)