Jab acceptable during training (4)
I believe the answer is:
poke
'jab' is the definition.
(synonyms)
'acceptable during training' is the wordplay.
'acceptable' becomes 'ok' ().
'during' is an insertion indicator.
'training' becomes 'pe'.
'ok' inserted within 'pe' is 'POKE'.
(Other definitions for poke that I've seen before include "Probe with stick" , "bag" , "Prod with a sharp object" , "Jab (with a finger)" , "Jab - old type of bonnet" .)