Straight bananas for sale with EC regulators' backing (2,3,4,5)
I believe the answer is:
as the crow flies
'straight' is the definition.
(I've seen this before)
'bananas for sale with ec regulators' backing' is the wordplay.
'bananas' indicates an anagram (bananas can informally mean crazy).
'backing' says to take the final letters.
The final letter of 'regulators' is 's'.
'for'+'sale'+'with'+'ec'='forsalewithec'
'forsalewithec' is an anagram of 'asthecrowflie'.
'asthecrowflie'+'s'='AS THE CROW FLIES'
(Other definitions for as the crow flies that I've seen before include "How rook moves" , "move in a straight line" , "without deviating" , "Directly" , "By direct route" .)