Used to be cut up (3)
I believe the answer is:
was
'used to be' is the definition.
(eg 'he was...' means 'he used to be...')
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for was that I've seen before include "Existed in the past" , "(I/he/she/it) existed" , "'Is, in the past (3)'" , "(I/he) existed" , "Used to be" .)