Hurry to succeed, lacking patience (4,2,6)
I believe the answer is:
make it snappy
'hurry' is the definition.
(phrased used to tell someone to hurry)
'succeed lacking patience' is the wordplay.
'succeed' becomes 'make it' (making it is a kind of succeeding).
'lacking patience' becomes 'snappy' (snappy can mean impatient or irritated).
'makeit'+'snappy'='MAKE IT SNAPPY'
'to' is the link.
(Other definitions for make it snappy that I've seen before include "Hurry up! (slang)" , "step on it" , "Get a move on!" , "Come along" , "To annoy a dog, perhaps" .)