Bogged down as stag may be seasonally? (2,1,3)
I believe the answer is:
in a rut
I believe this clue is a double definition.
'bogged down' is the first definition.
(both can mean in an uninspiring period or routine)
'as stag may be seasonally?' is the second definition.
(stags rut annually in order to mate)
(Other definitions for in a rut that I've seen before include "proceeding predictably" , "Following a tedious routine" , "Routinely stuck" , "Bogged down by tedium" , "Involved with boring routine" .)