With spirit lacking, heart lost at the expected time (4)
I believe the answer is:
duly
'at the expected time' is the definition.
(I've seen this in another clue)
'with spirit lacking heart lost' is the wordplay.
'with spirit lacking' becomes 'dully' (dull can mean without spirit or excitement).
'heart lost' means to remove the middle letters.
'dully' with its centre taken out is 'DULY'.
(Other definitions for duly that I've seen before include "As might be expected" , "In proper form, time" , "Following proper procedure" , "As a matter of course" , "Suitably" .)