Fair-haired British duke in isolated environment (6)
I believe the answer is:
blonde
'fair-haired' is the definition.
(I've seen this before)
'british duke in isolated environment' is the wordplay.
I cannot quite understand how this works, but
'british' could be 'b' (abbreviation e.g. in 'BBC') and 'b' is found in the answer.
'duke' could be 'd' (abbreviation) and 'd' is located in the answer.
'isolated' could be 'lone' (both can mean alone) and 'lone' is present in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for blonde that I've seen before include "Kind of girl that gentlemen are said to prefer" , "Flaxen" , "What may follow Strawberry" , "Kind of fair girl" , "Of a woman, having fair hair (6)" .)