Support runner-up getting a tick (6)
I believe the answer is:
second
This clue is a triple definition!
'support' is the first definition.
(seconding is a kind of supporting)
'runner-up' is the second definition.
(I've seen this before)
'getting' acts as a link.
'a tick' is the third definition.
(I've seen this before)
(Other definitions for second that I've seen before include "Support - runner-up" , "Eighty six thousand and four hundredth of a day" , "tick" , "Back-up; short time" , "Between first and third" .)