Remember to phone again (6)
I believe the answer is:
recall
I believe this clue is a double definition.
'remember' is the first definition.
(to recall something is to remember it)
'phone again' is the second definition.
('call' can be a synonym for 'phone' so perhaps 'recall' is OK for 'phone again')
'to' is the link.
(Other definitions for recall that I've seen before include "Summon to return" , "order to come back" , "Remember; demand back" , "Hark back" , "Order to return" .)