Removal of has-been gaining measure of acceptability (10)
I believe the answer is:
extraction
'removal' is the definition.
(I know that extraction is a type of removal)
'of has-been gaining measure of acceptability' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is found within the answer.
'measure' could be 'act' (I've seen this in another clue) and 'act' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for extraction that I've seen before include "breeding" , "Ethnic origin" , "one suffers with mouth open?" , "drawing" , "Dental operation" .)