Falsely superior large loaf has seeds occasionally (9)
I believe the answer is:
bigheaded
'falsely superior' is the definition.
(bigheaded means feeling superior undeservedly)
'large loaf has seeds occasionally' is the wordplay.
'large' becomes 'big' (synonyms).
'loaf' becomes 'head' (slang term).
'has' says to put letters next to each other.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternate letters of 'seeds' are 'ed'.
'big'+'head'+'ed'='BIGHEADED'
(Another definition for bigheaded that I've seen is " Conceited with large cranium".)