Ardent, even after a weekend (4)
I believe the answer is:
keen
'ardent' is the definition.
(I've seen this before)
'even after a weekend' is the wordplay.
'even' becomes 'e'en' (synonyms).
'after' says to put letters next to each other.
'a weekend' becomes 'k' (I've seen this in other clues).
'een' put 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" .)