Small heartless woman consuming free evening (7)
I believe the answer is:
sundown
'evening' is the definition.
(thesaurus)
'small heartless woman consuming free' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'heartless' means to remove the middle letters.
'consuming' means one lot of letters goes inside another.
'free' becomes 'undo' (I've seen this before**).
'woman' with its middle removed is 'wn'.
's'+'wn'='swn'
'swn' placed around 'undo' is 'SUNDOWN'.
(Other definitions for sundown that I've seen before include "Part of evening" , "Feature of evening" , "Event seen in evening" , "End of the day" , "Setting time" .)