Lacking polish, like this second def (10)
I believe the answer is:
unfinished
'lacking polish' is the definition.
'like this second def' is the wordplay.
I cannot quite understand how this works, but
'like' could be 'ish' ('ish' can be similar in meaning to 'like') and 'ish' is found within the answer.
'second' could be 'd' and 'd' is found within the answer.
The remaining letters 'unfine' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for unfinished that I've seen before include "Schubert's Eighth, for example" , "Not concluded" , "rough" , "3 18 ... in B minor" .)