Nasal problem: factor in blood disorder is in it (8)
I believe the answer is:
rhinitis
'nasal problem' is the definition.
'factor in blood disorder is in it' is the wordplay.
'factor in blood' becomes 'rh' (abbreviation for Rhesus factor).
'disorder' indicates anagramming the letters (I've seen 'diseased' mean this (I've seen this in other clues)).
'is'+'in'+'it'='isinit'
'isinit' with letters rearranged gives 'initis'.
'rh'+'initis'='RHINITIS'
(Other definitions for rhinitis that I've seen before include "I hint, sir, about a nose inflammation" , "trouble with the beak" , "Nasal inflammation" , "Inflammation of the lining of the nose" , "nasal affliction" .)