Quick bit of fun during physical training (6)
I believe the answer is:
prompt
'quick' is the definition.
(I know that quick can be written as prompt)
'fun during physical training' is the wordplay.
'fun' becomes 'romp' (I have seen 'sexy fun' mean 'romp' so perhaps 'fun' could also mean 'romp').
'during' indicates putting letters inside.
'physical training' becomes 'PT' (Physical Training).
'romp' put inside 'pt' is 'PROMPT'.
'bit of' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for prompt that I've seen before include "Immediate - supply actor's lines" , "Help forgetful actor with lines" , "Give hint as to actor who has forgotten lines (6)" , "effective in expedition" , "Quick, without delay" .)