Most recent part of the mine workings (3)
I believe the answer is:
new
'most recent' is the definition.
'new' can be an answer for 'recent' (similar in meaning). I am not sure about the 'most' bit.
'part of the mine workings' is the wordplay.
'part of' says the answer is hidden in the clue.
'NEW' is hidden within 'the mine workings'.
Can you help me to learn more?
(Other definitions for new that I've seen before include "Recently made, etc" , "Modern" , "Seen for the first time" , "Unfamiliar, restored" , "Unconventional" .)