Slipped disc, finally sent up on last pair of crutches (7)
I believe the answer is:
escaped
'slipped' is the definition.
(slip can mean to escape or get away)
'disc finally sent up on last pair of crutches' is the wordplay.
I cannot quite see how this works, but
'sent up' could be 'aped' (ape can mean to send up or imitate) and 'aped' is found within the answer.
The remaining letters 'esc' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for escaped that I've seen before include "gone!" , "Ran away from confinement" , "Got away from captors" , "Got away, broke loose" , "Fled from captivity" .)