Some vague student invited one (5)
I believe the answer is:
guest
'one' is the definition.
Both the definition and answer are adjectives. Perhaps there's a link between them I don't understand?
'some vague student invited' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'GUEST' can be found hidden inside 'vague student invited'.
Can you help me to learn more?
(Other definitions for guest that I've seen before include "Caller" , "Invited person" , "Someone invited" , "Person receiving another's hospitality" , "Hotel resident" .)