Needs to be in phase (3)
I believe the answer is:
has
'needs' is the definition.
('have' can be a synonym of 'need')
'in phase' is the wordplay.
'in' says the answer is hidden in the clue.
'HAS' is hidden in the letters of 'phase'.
'to be' acts as a link.
(Other definitions for has that I've seen before include "suffers from" , "Enjoys" , "Eats" , "Possesses or owns" , "Bears" .)