Join up broken tinsel (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
enlist
'join up' is the definition.
(I've seen this before)
'broken tinsel' is the wordplay.
'broken' indicates anagramming the letters.
'tinsel' anagrammed gives 'ENLIST'.
(Other definitions for enlist that I've seen before include "Listen (anag.)" , "Join up in silent way" , "Join the armed services" , "Sign on -- 13 (anag)" , "Join up - tinsel (anag)" .)