Unproductive day after upturn implies decline (5)
I believe the answer is:
droop
'decline' is the definition.
(I've seen this before)
'unproductive day after upturn' is the wordplay.
'unproductive' becomes 'poor' (synonyms).
'day' becomes 'd' (abbreviation for day).
'after' says to put letters next to each other.
'upturn' is a reversal indicator (in a down clue, letters go up).
'poor'+'d'='poord'
'poord' backwards is 'DROOP'.
'implies' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for droop that I've seen before include "Flag" , "Sag downwards" , "Hang downwards, lose strength or spirit" , "Become limp" , "Hang limply" .)