Shade one doing manoeuvres (6)
I believe the answer is:
indigo
'shade' is the definition.
(shade of blue)
'one doing manoeuvres' is the wordplay.
'one' becomes 'I' (Roman numeral).
'manoeuvres' indicates anagramming the letters.
'doing' anagrammed gives 'ndigo'.
'i'+'ndigo'='INDIGO'
(Other definitions for indigo that I've seen before include "Blue-violet colour" , "type of dye" , "Spectral colour" , "product of woad" , "Settlement; New Mexico native" .)