Two take time to go on wagon (5)
I believe the answer is:
twain
'two' is the definition.
(archaic term for 'two')
'time to go on wagon' is the wordplay.
'time' becomes 't' (abbreviation).
'to go on' means one lot of letters go next to another (in a down clue, some letters go on top of others).
'wagon' becomes 'wain' (wain is a kind of wagon).
't'+'wain'='TWAIN'
'take' is the link.
(Other definitions for twain that I've seen before include "I want (anag) - US novelist and humorist" , "Archaic term for two" , "Mark, say" , "Mark ___ , American writer" , "Mark . . . . . was the pen name of Samuel Langhorne Clemens" .)