Join up with fancy tinsel (6)
I believe the answer is:
enlist
'join up' is the definition.
(I've seen this in another clue)
'fancy tinsel' is the wordplay.
'fancy' indicates an anagram.
'tinsel' with letters rearranged gives 'ENLIST'.
'with' is the link.
(Other definitions for enlist that I've seen before include "Join the military" , "Join up, sign on" , "Listen (anag.)" , "augment army" , "Join up in silent way" .)