Being injured is shock, little good (5)
I believe the answer is:
stung
'being injured' is the definition.
('stung' can be similar in meaning to 'injured')
'shock little good' is the wordplay.
'shock' becomes 'stun' (both can mean to surprise).
'little' indicates taking the first letters.
The initial letter of 'good' is 'g'.
'stun'+'g'='STUNG'
'is' is the link.
(Other definitions for stung that I've seen before include "Punctured eg by wasp" , "cheated" , "Caused sharp pain" , "Bitten, pierced" , "Wounded by a bee or wasp" .)