Square set enfolding outside square? (7)
I believe the answer is:
sixteen
'square' is the definition.
(sixteen is a square number)
'set enfolding outside square?' is the wordplay.
'set enfolding' becomes 'sixte' (I can't explain this - if you can you should give a lot more credence to this answer).
'outside' means to remove the middle letters (I've seen 'outside of' mean this).
'square?' becomes 'even' (both mean 'owing nothing' as in 'we're all square').
'even' with its middle removed is 'en'.
'sixte'+'en'='SIXTEEN'
Can you help me to learn more?
(Other definitions for sixteen that I've seen before include "Old song: 'When you were sweet .......'" , "Fourth power of two" , "Sweet Little -, (Chuck Berry)" , "XVI" , "Four squared" .)