Call to follow possum (8)
I believe the answer is:
ringtail
'possum' is the definition.
(I've seen this before)
'call to follow' is the wordplay.
'call' becomes 'ring' (telephone call).
'to follow' becomes 'tail' (both can mean to chase or pursue).
'ring'+'tail'='RINGTAIL'
(Other definitions for ringtail that I've seen before include "Possum" , "Type of cat" , "creature" , "Sleepwalker" , "Sort of cat" .)