Puts up with market pessimists (5)
I believe the answer is:
bears
This clue is a double definition.
'puts up with' is the first definition.
('bear' can be a synonym of 'put up with')
'market pessimists' is the second definition.
(I've seen this in another clue)
(Other definitions for bears that I've seen before include "Carries" , "Ursine animals" , "Massive mammals with shaggy coats" , "Large animals, polar or brown" , "Big animals" .)