Accept trouble with physical training (5)
I believe the answer is:
adopt
'accept' is the definition.
(adopting is a kind of accepting)
'trouble with physical training' is the wordplay.
'trouble' becomes 'ado' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'physical training' becomes 'pt'.
'ado'+'pt'='ADOPT'
(Other definitions for adopt that I've seen before include "Take on (another's child)" , "Embrace" , "choose as candidate" , "Take up, follow" , "Start to wear" .)