Uncultivated region where angry sea eagles start to squabble (10)
I believe the answer is:
wilderness
'uncultivated region' is the definition.
(wild, uncultivated land)
'angry sea eagles start to squabble' is the wordplay.
'angry' becomes 'wild' (synonyms).
'sea eagles' becomes 'ernes' (erne is a kind of sea eagle).
'start to' says to take the initial letters.
The first letter of 'squabble' is 's'.
'wild'+'ernes'+'s'='WILDERNESS'
'where' acts as a link.
(Other definitions for wilderness that I've seen before include "for a time unrecognised" , "Inhospitable region" .)