Isolated individual, fellow on manoeuvres (4,4)
I believe the answer is:
lone wolf
'isolated individual' is the definition.
'fellow on manoeuvres' is the wordplay.
'manoeuvres' indicates anagramming the letters.
'fellow'+'on'='fellowon'
'fellowon' anagrammed gives 'LONE-WOLF'.
(Other definitions for lone wolf that I've seen before include "One avoids the company the others" , "He likes to operate by himself" , "Solitary type" , "one preferring his own company" , "Solitary person" .)