Warms sweetheart wearing top coverings (5)
I believe the answer is:
heats
'warms' is the definition.
(I've seen this in another clue)
'sweetheart wearing top coverings' is the wordplay.
'sweetheart wearing' becomes 'he' (I can't justify this - if you can you should give a lot more credence to this answer).
'top' means to remove the first letter.
'coverings' becomes 'mats' (mat is a kind of covering).
'mats' with its initial letter taken off is 'ats'.
'he'+'ats'='HEATS'
Can you help me to learn more?
(Other definitions for heats that I've seen before include "Eliminating rounds of a race" , "Makes hot or warm" , "Warms up for the preliminary races" , "Eliminating rounds in a contest" , "Haste (anag.)" .)