One going on record wants pen, mostly drunk (6)
I believe the answer is:
stylus
'one going on record' is the definition.
(I've seen this before)
'wants pen mostly drunk' is the wordplay.
'wants pen' becomes 'sty' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mostly' means to remove the last letter (most but not all of the word).
'drunk' becomes 'lush' (lush is a kind of drunk).
'lush' with its last letter taken off is 'lus'.
'sty'+'lus'='STYLUS'
Can you help me to learn more?
(Other definitions for stylus that I've seen before include "writer" , "Old gramophone needle" , "LP record pick-up" , "LP tracker" , "Vinyl records needle" .)