Companion on trip in pink (6,9)
I believe the answer is:
fellow traveller
I believe this clue is a double definition.
'companion on trip' is the first definition.
'pink' is the second definition.
(term for a supporter of communist ideals)
'in' is the link.
(Other definitions for fellow traveller that I've seen before include "one with leftist leanings" , "Leftist sympathiser" , "left supporter" , "Communist sympathiser" , "Like monk for nun in Chaucer, for example" .)