Promotion by Northern Irish making deep point (5)
I believe the answer is:
nadir
'deep point' is the definition.
'nadir' can be an answer for 'point' (I have seen 'Low point' mean 'nadir' so perhaps 'point' could also mean 'nadir'). I'm unsure of the 'deep' bit.
'promotion by northern irish' is the wordplay.
'promotion' becomes 'ad' (short for advert).
'by' means one lot of letters go next to another.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'irish' becomes 'IR' (abbreviation).
'ad' put after 'n' is 'nad'.
'nad'+'ir'='NADIR'
'making' acts as a link.
Can you help me to learn more?
(Other definitions for nadir that I've seen before include "pits" , "Very bottom, farthest from zenith" , "Drain to lowest level" , "Lower one cannot get!" , "It's the depths" .)