Not all isolated? (5)
I believe the answer is:
apart
'isolated?' is the definition.
(I know that isolated can be written as apart)
'not all' is the wordplay.
I cannot really understand how this works, but
'not all' could be 'part' ('part' is the opposite to 'all') and 'part' is present in the answer.
A single letter 'a' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for apart that I've seen before include "aloof" , "Separated physically" , "Estranged - in pieces" , "Independently" , "Separated or at a distance" .)