Relative seen during south-east river walk (7)
I believe the answer is:
saunter
'walk' is the definition.
(I know that saunter is a type of walk)
'relative seen during south-east river' is the wordplay.
'relative' becomes 'aunt' (aunt is a type of relative).
'seen during' means one lot of letters goes inside another.
'south east' becomes 'SE' (abbreviation).
'river' becomes 'r' (abbreviation).
'aunt' going inside 'se' is 'saunte'.
'saunte'+'r'='SAUNTER'
(Other definitions for saunter that I've seen before include "Leisurely stroll" , "Walk in a leisurely way" , "Walk casually or jauntily" , "Amble along" , "'Amble, stroll (7)'" .)