Former writer baled up but deemed non-essential (10)
I believe the answer is:
expendable
'deemed non-essential' is the definition.
I can't judge whether this defines the answer.
'former writer baled up' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'writer' becomes 'pen' (something which writes).
'up' indicates an anagram (letters get chucked up).
'baled' with letters rearranged gives 'dable'.
'ex'+'pen'+'dable'='EXPENDABLE'
'but' is the link.
Can you help me to learn more?
(Other definitions for expendable that I've seen before include "Able to be sacrificed" , "Easily abandoned" , "not important" , "Easily sacrificed" .)