Training expert in silence, perhaps (5)
I believe the answer is:
peace
'silence perhaps' is the definition.
(silence is a peaceful state)
'training expert' is the wordplay.
'training' becomes 'PE' (Physical Education).
'expert' becomes 'ace' (ace can informally mean very good).
'pe'+'ace'='PEACE'
'in' acts as a link.
(Other definitions for peace that I've seen before include "Quiet - lack of warfare" , "[STILLNESS]" , "still?" , "Repose, tranquillity" , "Absence of conflict" .)