Walk or stroll by river (6)
I believe the answer is:
ramble
'walk' is the definition.
(I've seen this before)
'stroll by river' is the wordplay.
'stroll' becomes 'amble' ('amble' can be a synonym of 'stroll').
'by' is a charade indicator (letters next to each other).
'river' becomes 'r'.
'amble' put after 'r' is 'RAMBLE'.
'or' is the link.
(Other definitions for ramble that I've seen before include "Walk for pleasure or talk confusingly" , "Walk desultorily (or in a group)" , "Walk for pleasure or stray from subject" , "Show incoherence" , "Walk in the country - talk aimlessly at length" .)