Colour round head of Davy Jones (6)
I believe the answer is:
indigo
'colour' is the definition.
(indigo is a kind of colour)
'round head of davy jones' is the wordplay.
'round' indicates putting letters inside.
'head of' suggests taking the first letters.
'jones' becomes 'inigo' (inigo jones).
The first letter of 'davy' is 'd'.
'd' put within 'inigo' is 'INDIGO'.
(Other definitions for indigo that I've seen before include "Spectral colour" , "Deep violet-blue colour" , "Blue-violet colour" , "I of ROYGBIV" , "Colour - I'd go in (anag)" .)