Wade about in a Scottish river for sport (8)
I believe the answer is:
speedway
'sport' is the definition.
(I've seen this before)
'wade about in a scottish river' is the wordplay.
'about' indicates anagramming the letters.
'in' is an insertion indicator.
'a scottish river' becomes 'spey' (I've seen this before).
'wade' anagrammed gives 'edwa'.
'edwa' going within 'spey' is 'SPEEDWAY'.
'for' acts as a link.
(Other definitions for speedway that I've seen before include "Dirt track motorcycle racing" , "Race-track" , "fast-track competition" , "SPORT/GAME" , "Stadium for motorcycle racing" .)