Labour man, not posh, could be strange (8)
I believe the answer is:
abnormal
'strange' is the definition.
(both can mean unusual)
'labour man not posh could be' is the wordplay.
'not' indicates named letters should be taken away.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'could be' indicates anagramming the letters.
'labour'+'man'='labourman'
'labourman' with 'u' removed is 'laborman'.
'laborman' anagrammed gives 'ABNORMAL'.
(Other definitions for abnormal that I've seen before include "Different to what is ordinary or expected" , "Odd" , "The reverse of 32 Across" , "Deviating from the standard" , "Exceptional; strange" .)