Not at home on a middle-class street (4)
I believe the answer is:
away
'not at home' is the definition.
(I've seen this before)
'on a middle-class street' is the wordplay.
'on' means one lot of letters go next to another.
'a middle' says to take the centre.
'street' becomes 'way' (I've seen this before).
The central letter of 'class' is 'a'.
'a' put next to 'way' is 'AWAY'.
(Other definitions for away that I've seen before include "constantly" , "(Of sports fixture) at opponents' ground" , "Not at home, somewhere else" , "Elsewhere" , "On vacation" .)