Go on a walk (6)
I believe the answer is:
ramble
I believe this is a double definition.
'go on' is the first definition.
(rambling is a kind of going on)
'a walk' is the second definition.
(ramble is a kind of walk)
(Other definitions for ramble that I've seen before include "Walk as leisure activity" , "Show incoherence" , "Walk for pleasure or stray from subject" , "Walk; be discursive" , "Go as fancy leads" .)