Capacious container (or ancient outbuilding?) (7)
I believe the answer is:
holdall
'capacious container' is the definition.
'holdall' can be an answer for 'container' (holdall is a kind of container). I am not sure about the 'capacious' bit.
'ancient outbuilding?' is the wordplay.
I cannot quite see how this works, but
'ancient' could be 'old' (similar in meaning) and 'old' is present in the answer.
The remaining letters 'hall' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'or' acts as a link.
Can you help me to learn more?
(Other definitions for holdall that I've seen before include "retainer" , "Large bag (no need for another?)" , "Large case, with handles" , "Large carrying bag" , "Large strong bag with handles or shoulder strap" .)