Answer - well it's not in new X-ray relating to the armpit (8)
I believe the answer is:
axillary
'answer well it's not in new x-ray relating to the armpit' is the definition.
I know that 'armpit' relates to this answer.
'relating to the armpit' is the wordplay.
'relating' becomes 'ry' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'the armpit' becomes 'axilla' ('axilla' can be a synonym of 'armpit').
'ry' put after 'axilla' is 'AXILLARY'.
Can you help me to learn more?
(Another definition for axillary that I've seen is " of the armpit".)