Remember a suspicious caller (6)
I believe the answer is:
recall
'remember' is the definition.
(to recall something is to remember it)
'a suspicious caller' is the wordplay.
'a suspicious' indicates an anagram (an unusual or suspect spelling).
'caller' with letters rearranged gives 'RECALL'.
(Other definitions for recall that I've seen before include "cancel" , "Summon back, perhaps to mind" , "Summon back as to memory" , "Don''t forget - come again" , "Evoke" .)