To join up the various lines takes time (6)
I believe the answer is:
enlist
'to join up' is the definition.
(I've seen this before)
'the various lines takes time' is the wordplay.
'the various' indicates an anagram.
'takes time' becomes 't' (I've seen this in other clues).
'lines' with letters rearranged gives 'enlis'.
'enlis'+'t'='ENLIST'
(Other definitions for enlist that I've seen before include "Enrol in the services" , "Listen (anag.)" , "Join the armed services" , "Join the military" , "Draft" .)