A plan's arranged, not initially paying through the nose (5)
I believe the answer is:
nasal
'through the nose' is the definition.
(nasal means relating to the nose)
'a plan's arranged not initially paying' is the wordplay.
'a plan's' indicates anagramming the letters (plan can mean organise).
'initially' indicates taking the first letters.
'paying' becomes 'sal' (I can't explain this - if you can you should believe this answer much more).
The initial letters of 'arranged not' is 'an'.
'an' with letters rearranged gives 'na'.
'na'+'sal'='NASAL'
Can you help me to learn more?
(Other definitions for nasal that I've seen before include "piece of armour" , "description of Alain's vowels" , "Describing some hooter" , "Pertaining to the nose" , "front piece of helmet" .)