Ardent, even after a weekend (4)
I believe the answer is:
keen
'ardent' is the definition.
(I've seen this in another clue)
'even after a weekend' is the wordplay.
'even' becomes 'e'en' (old-fashioned contraction).
'after' says to put letters next to each other.
'a weekend' becomes 'k' (I've seen this in other clues).
'een' after 'k' is 'KEEN'.
(Other definitions for keen that I've seen before include "Fierce - sharp" , "Penetrating; ardent" , "Longing" , "Enthusiastic or sharp" , "Sharp -- express grief" .)