Gold chain seen in bourse regularly (5)
I believe the answer is:
ochre
'gold' is the definition.
(I've seen this before)
'chain seen in bourse regularly' is the wordplay.
'chain' becomes 'ch' (abbreviation for the unit of length).
'seen in' means one lot of letters goes inside another.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'bourse' are 'ore'.
'ch' going into 'ore' is 'OCHRE'.
(Other definitions for ochre that I've seen before include "Earthy pigment - light brownish-yellow" , "Earth used in pigments" , "yellowish-red" , "Orange" , "Orange-yellow colour" .)