Old army outfit, say, gathered by hero (6)
I believe the answer is:
legion
'old army' is the definition.
'legion' can be an answer for 'army' (legion is a kind of army). I'm unsure of the 'old' bit.
'outfit say gathered by hero' is the wordplay.
I cannot quite understand how this works, but
'say' could be 'eg' (both can mean 'for example') and 'eg' is located in the answer.
'hero' could be 'lion' (lion can mean a brave person) and 'lion' is present in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for legion that I've seen before include "Large unit of the old Roman army" , "Roman military formation" , "France has a foreign one" , "Military force - in Lego (anag)" , "Body of Roman or French soldiers" .)