A guy skirting river gets lost (6)
I believe the answer is:
astray
'lost' is the definition.
(thesaurus)
'a guy skirting river' is the wordplay.
'guy' becomes 'stay' (I've seen this before**).
'skirting' indicates putting letters inside.
'river' becomes 'r'.
'stay' placed around 'r' is 'stray'.
'a'+'stray'='ASTRAY'
'gets' is the link.
(Other definitions for astray that I've seen before include "In a lost state" , "wrong way" , "Gone off the right path" , "Off one's route or lost" , "Away from the right path like a satyr (6)" .)