Talk about exercises in action (9)
I believe the answer is:
operation
'action' is the definition.
(operation is a kind of action)
'talk about exercises' is the wordplay.
'talk' becomes 'oration'.
'about' indicates putting letters inside.
'exercises' becomes 'pe'.
'oration' placed around 'pe' is 'OPERATION'.
'in' acts as a link.
(Other definitions for operation that I've seen before include "military undertaking" , "Action; process" , "Manoeuvre - military action" , "Procedure; enterprise" , "Act of surgery" .)