Visitor to bank, perhaps, left in indignation (6)
I believe the answer is:
angler
'visitor to bank perhaps' is the definition.
(an angler might fish at a river bank)
'left in indignation' is the wordplay.
'left' becomes 'L' (common abbreviation).
'in' is an insertion indicator.
'indignation' becomes 'anger' (indignant anger).
'l' inserted within 'anger' is 'ANGLER'.
(Other definitions for angler that I've seen before include "who looks for compliments" , "A rod and line fisherman" , "A rod-and-line fisherman" , "Fisher with hook and line." , "One proverbially exaggerating" .)