Take a long walk with thriller writer, right to the top (6)
I believe the answer is:
ramble
'take a long walk' is the definition.
'right to the top' is the wordplay.
'right' becomes 'r' (common abbreviation).
'to the top' becomes 'amble' (I can't explain this - if you can you should believe this answer much more).
'r'+'amble'='RAMBLE'
'with thriller writer' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for ramble that I've seen before include "Walk; be discursive" , "Walk as leisure activity" , "Walk for pleasure or stray from subject" , "Walk for pleasure or talk confusingly" , "Take a country walk" .)