As soon as you see round, things are different (2,5)
I believe the answer is:
on sight
'as soon' is the definition.
I know nothing about this answer so I can't judge whether this works.
'you see round things are different' is the wordplay.
'see round' says to take the centre.
'are different' indicates an anagram.
The middle letter of 'you' is 'o'.
'things' with letters rearranged gives 'nsight'.
'o'+'nsight'='ON SIGHT'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for on sight that I've seen before include "How good musicians can play" , "when observed" , "without a second glance?" , "As soon as seen" , "As soon as presented" .)