Make certain to follow right in (6)
I believe the answer is:
ensure
'make certain' is the definition.
(synonyms)
'follow right in' is the wordplay.
'follow' becomes 'ensue' (ensue can mean to follow or happen as a result).
'right' becomes 'r' (common abbreviation).
'in' indicates putting letters inside.
'ensue' placed around 'r' is 'ENSURE'.
'to' acts as a link.
(Other definitions for ensure that I've seen before include "Make certain that (something occurs)" , "Make certain (something will occur)" , "Make certain for the future" , "warrant" , "Guarantee" .)