Howls at trees (4)
I believe the answer is:
I believe this is a double definition.
'howls' is the first definition.
(I've seen this in another clue)
'trees' is the second definition.
(bay is a type of tree)
'at' is the link.
(Other definitions for bays that I've seen before include "Inlets; barks" , "Indentations of a shoreline" , "Laurel trees" .)