If coming back in poor visibility, you may find a square peg (6)
I believe the answer is:
misfit
'a square peg' is the definition.
(I've seen this in another clue)
'if coming back in poor visibility' is the wordplay.
'coming back' shows that the letters should be reversed in order.
'in' is an insertion indicator.
'poor visibility' becomes 'mist' (mist causes poor visibility).
'if' written backwards gives 'fi'.
'fi' put within 'mist' is 'MISFIT'.
'you may find' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for misfit that I've seen before include "One can't adapt to their circumstances" , "Someone not suited" , "An unsuitable thing" , "Weirdo" , "Maverick, nonconformist" .)