Grumpy guy, rogue ticket seller, coming across resistance (5)
I believe the answer is:
trout
'grumpy guy' is the definition.
(trout can mean a grumpy person)
'rogue ticket seller coming across resistance' is the wordplay.
'rogue ticket seller' becomes 'tout' (as in a ticket tout).
'coming across' means one lot of letters goes inside another.
'resistance' becomes 'r' (electronics abbreviation).
'tout' enclosing 'r' is 'TROUT'.
(Other definitions for trout that I've seen before include "Game fish related to salmon" , "Rainbow, say" , "Edible fish" , "Performance by five players" , "Mistiness" .)