Remember to telephone again? (6)
I believe the answer is:
recall
I believe this is a double definition.
'remember' is the first definition.
(to recall something is to remember it)
'telephone again?' is the second definition.
('call' can be a synonym for 'telephone' so perhaps 'recall' is OK for 'telephone again')
'to' is the link.
(Other definitions for recall that I've seen before include "Summon back, perhaps to mind" , "cancel" , "Hark back" , "Summon back or bring to mind" , "Summon back as to memory" .)