Adhere (5)
(Other definitions for cling that I've seen before include "Hold tightly, become attached" , "Hold, cleave" , "Be emotionally over-dependent" , "Grasp urgently" , "Stick - tinkle" .)
'adhere' is the definition.
(I know that adhere can be written as stick)
This is the entire clue.
(Other definitions for stick that I've seen before include "Flak - cling" , "Gear lever; adhere" , "Rod" , "Staff - criticism" , "Join firm" .)