Qualifier, Jet, overwhelmed with advice (9)
I believe the answer is:
adjective
'qualifier' is the definition.
(adjective is a kind of qualifier)
'jet overwhelmed with advice' is the wordplay.
'overwhelmed with' indicates anagramming the letters (overwhelm can mean to confuse).
'jet' anagrammed with 'advice' makes 'ADJECTIVE'.
(Other definitions for adjective that I've seen before include "Qualifying or descriptive part of speech" , "Descriptive word" , "It qualifies a noun" , "Word qualifying a noun" , "Word added to noun to qualify meaning" .)