Playful remarks may be injurious in time (8)
I believe the answer is:
badinage
'playful remarks may' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'injurious in time' is the wordplay.
'injurious' becomes 'bad' (I've seen this in another clue).
'time' becomes 'age' (an age is a period of time).
'bad'+'in'+'age'='BADINAGE'
'be' is the link.
Can you help me to learn more?
(Other definitions for badinage that I've seen before include "Good-natured banter or teasing" , "A big Dane given to banter" , "Backchat, banter" , "Beg Diana with good-humoured teasing" , "Raillery, give-and-take" .)