As naval fighter, put on a shade of blue (10)
I believe the answer is:
aquamarine
'shade of blue' is the definition.
'as naval fighter put on a' is the wordplay.
'as' becomes 'qua' (I've seen this before).
'naval fighter' becomes 'marine'.
'put on' means one lot of letters go next to another.
'qua'+'marine'='quamarine'
'quamarine' after 'a' is 'AQUAMARINE'.
(Other definitions for aquamarine that I've seen before include "Pale bluish-green" , "Bluish-green colour" , "Greenish blue" , "Gem" , "Beryl" .)