Stories of my religious studies must omit Spain (9)
I believe the answer is:
mythology
'stories' is the definition.
(thesaurus)
'my religious studies must omit spain' is the wordplay.
'religious studies' becomes 'theology' (I've seen this before).
'must omit' indicates named letters should be taken away.
'spain' becomes 'e' (abbreviation for Espana).
'theology' with 'e' removed is 'thology'.
'my'+'thology'='MYTHOLOGY'
'of' is the link.
(Other definitions for mythology that I've seen before include "Legends and sagas, in general" , "Legend" , "Body of old fables" , "Study of ancient tales of gods and heroes" .)