Son died going after brown bear (5)
I believe the answer is:
stand
'bear' is the definition.
('stand' can be a synonym of 'bear')
'son died going after brown' is the wordplay.
'son' becomes 's'.
'died' becomes 'd'.
'going after' means one lot of letters go next to another.
'brown' becomes 'tan' (tan is a kind of brown).
'd' put after 'tan' is 'tand'.
's'+'tand'='STAND'
(Other definitions for stand that I've seen before include "principled position" , "Tolerate; rise" , "Remain upright" , "Platform; attitude" , "stay the same in position" .)