Some guy at terrific talk (6)
I believe the answer is:
yatter
'talk' is the definition.
(to yatter is to talk or chatter)
'some guy at terrific' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'YATTER' is hidden within 'guy at terrific'.
(Other definitions for yatter that I've seen before include "conversation" , "Talk idly" , "Talk endlessly about nothing" , "Go on and on" , "rabbit on endlessly" .)