Joined one inside and exercised (7)
I believe the answer is:
wielded
'exercised' is the definition.
(wield can mean to use or exercise)
'joined one inside' is the wordplay.
I cannot really understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'joined' could be 'welded' (welding is a kind of joining) and 'welded' is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'and' is the link.
Can you help me to learn more?
(Another definition for wielded that I've seen is " Exerted".)