Terrible time to swallow popular banter (8)
I believe the answer is:
badinage
'banter' is the definition.
(I know that badinage is a type of banter)
'terrible time to swallow popular' is the wordplay.
'terrible' becomes 'bad' (similar in meaning).
'time' becomes 'age' (an age is a period of time).
'to swallow' indicates putting letters inside.
'popular' becomes 'in' ('in' can mean trendy).
'bad'+'age'='badage'
'badage' enclosing 'in' is 'BADINAGE'.
(Other definitions for badinage that I've seen before include "Humorous banter" , "Beg Diana for light banter" , "Backchat, banter" , "Wordplay" , "Good-humoured banter (8)" .)