Spare space, as we see it, outside pub (6)
I believe the answer is:
skinny
'spare' is the definition.
(I've seen this before)
'it outside pub' is the wordplay.
'it' becomes 'sky' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'outside' means one lot of letters goes inside another (some letters go outside others).
'pub' becomes 'inn' (an inn is a type of pub).
'sky' placed around 'inn' is 'SKINNY'.
'space as we see' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for skinny that I've seen before include "Type of dip" , "Scraggy, scrawny" , "Unattractively thin" , "Tight-fitting" , "stout? Certainly not!" .)