Mother, I'm seriously hurt (4)
I believe the answer is:
maim
'seriously hurt' is the definition.
(I've seen this in another clue)
'mother i'm' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'i'm' becomes 'im' ().
'ma'+'im'='MAIM'
(Other definitions for maim that I've seen before include "Injure (a person), causing permanent disability" , "'Disable, mutilate (4)'" , "Cripple, mutilate" , "Wound and cripple" , "Injure permanently" .)