Drooping occasionally, fellow heads for potency problem years (6)
I believe the answer is:
floppy
'drooping' is the definition.
(I've seen this before)
'occasionally fellow heads for potency problem years' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'heads for' says to take the initial letters.
The first letters of 'potency problem years' is 'ppy'.
The alternating letters of 'fellow' are 'flo'.
'flo'+'ppy'='FLOPPY'
(Other definitions for floppy that I've seen before include "Not rigid" , "Limp - droopingLimp - drooping" , "Flexible computer disc" , "Tending to hang loosely" , "Opposed to firm" .)