Giant, one meeting a fairy queen (7)
I believe the answer is:
titania
'fairy queen' is the definition.
(thesaurus)
'giant one meeting a' is the wordplay.
'giant' becomes 'titan' ('titan' can be a synonym of 'giant').
'one' becomes 'i' (Roman numeral).
'meeting' says to put letters next to each other.
'titan'+'i'+'a'='TITANIA'
(Other definitions for titania that I've seen before include "Wife of Oberon (MND)" , "Oberon's better half?" , "in the D [DREAM] ..." , "asinine lover" , "Shakespeare's queen of the fairies" .)