One not suitable if brought up in poor visibility (6)
I believe the answer is:
misfit
'one not suitable' is the definition.
I can't tell whether this definition defines the answer.
'if brought up in poor visibility' is the wordplay.
'brought up' is a reversal indicator (in a down clue, letters go up).
'in' means one lot of letters goes inside another.
'poor visibility' becomes 'mist' (mist causes poor visibility).
'if' back-to-front is 'fi'.
'fi' put within 'mist' is 'MISFIT'.
Can you help me to learn more?
(Other definitions for misfit that I've seen before include "Fish out of water" , "Weirdo" , "Jerk" , "One who is out of place" , "Lone wolf" .)