Never stopping, 100 get no relief (9)
I believe the answer is:
ceaseless
'never stopping 100 get no relief' is the definition.
I can't judge whether this definition defines the answer.
'stopping 100 get no relief' is the wordplay.
'stopping' means one lot of letters goes inside another (inserted letters stop or plug a gap).
'l00' becomes 'C' (Roman numeral).
'get no' becomes 'less' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'relief' becomes 'ease' (I've seen this before).
'c'+'less'='cless'
'cless' placed around 'ease' is 'CEASELESS'.
Can you help me to learn more?
(Other definitions for ceaseless that I've seen before include "Continual" , "keeps on running" , "Constant and unending" , "Incessant, unremitting" , "Continuous" .)