Choose one colour, primarily, for drinks dispenser (5)
I believe the answer is:
optic
'drinks dispenser' is the definition.
(I've seen this before)
'choose one colour primarily' is the wordplay.
'choose' becomes 'opt' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'primarily' says to take the initial letters.
The initial letter of 'colour' is 'c'.
'opt'+'i'+'c'='OPTIC'
'for' acts as a link.
(Other definitions for optic that I've seen before include "Spirits measurer" , "Describing a sensory organ" , "Pub measuring device" , "Teacher's maybe dispensed with this" , "Visual" .)