Soldier on exercise about taking part (9)
I believe the answer is:
persevere
'soldier on' is the definition.
(I've seen this before)
'exercise about taking part' is the wordplay.
'exercise about' becomes 'pere' (I can't explain this - if you can you should give a lot more credence to this answer).
'taking' is an insertion indicator.
'part' becomes 'sever' (severing is a kind of parting).
'pere' placed around 'sever' is 'PERSEVERE'.
Can you help me to learn more?
(Other definitions for persevere that I've seen before include "Battle on" , "Be persistent, refuse to stop" , "Press on" , "Fight on" , "Soldier on" .)