Have a cold (3)
I believe the answer is:
ail
'have a cold' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ail that I've seen before include "Cause to feel indisposed" , "Worry" , "Trouble, afflict; be sickly" , "Be ill or unwell" , "Afflict -- feel unwell" .)