Massage is a problem (3)
I believe the answer is:
rub
This clue is a double definition.
'massage' is the first definition.
(rub can mean to massage)
'problem' is the second definition.
(rub can mean a problem or snag)
'is a' is the link.
(Other definitions for rub that I've seen before include "Massage or buff" , "Ointment; copy (a brass)" , "trouble" , "Remove marks - ... out" , "Polish by friction" .)