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' indicates the answer is hidden within the clue.
'HAS' can be found hidden inside 'phase'.
'to be' is the link.
(Other definitions for has that I've seen before include "suffers from" , "Enjoys" , "Eats" , "Possesses or owns" , "Bears" .)