Recent partner drops year-long growth upward (8)
I believe the answer is:
newlywed
'recent partner' is the definition.
(someone recently married)
'drops year-long growth upward' is the wordplay.
'drops year' becomes 'dewy' (I can't justify this - if you can you should give a lot more credence to this answer).
'long' becomes 'l'.
'growth' becomes 'wen' (wen can mean a skin growth).
'upward' says the letters should be written in reverse.
'dewy'+'l'+'wen'='dewylwen'
'dewylwen' in reverse letter order is 'NEWLYWED'.
(Other definitions for newlywed that I've seen before include "Bride or groom" , "One recently married" .)