Controversy in Scottish city after dumping fish (4)
I believe the answer is:
stir
'controversy' is the definition.
(as in causing a stir)
'scottish city after dumping fish' is the wordplay.
'scottish city' becomes 'stirling' (Stirling is a city in Scotland).
'after dumping' is a deletion indicator.
'fish' becomes 'ling' (ling is a kind of fish).
'stirling' with 'ling' removed is 'STIR'.
'in' is the link.
(Other definitions for stir that I've seen before include "Move around - prison" , "College" , "Stimulate; prison" , "riot" , "Agitate, arouse" .)