Loose cows on farm creating potentially tricky problem (3,2,5)
I believe the answer is:
can of worms
'potentially tricky problem' is the definition.
(a can of worms is a controversial topic)
'loose cows on farm' is the wordplay.
'loose' indicates an anagram (letters are loosened from their original positions).
'cows'+'on'+'farm'='cowsonfarm'
'cowsonfarm' anagrammed gives 'CAN OF WORMS'.
'creating' is the link.
(Other definitions for can of worms that I've seen before include "amateur angler's bait?" , "Something likely to prove awkward" , "Opening this could be problem" , "Complex problem" , "Bird's convenience food" .)