Claims, for instance, that Ella's mad about (7)
I believe the answer is:
alleges
'claims for instance that ella's mad about' is the definition.
'alleges' can be an answer for 'claims' (I've seen this in another clue). I'm not certain of the rest of the definition.
'that ella's mad about' is the wordplay.
'that' becomes 'ge' (I can't justify this - if you can you should give a lot more credence to this answer).
'mad' indicates an anagram.
'about' means one lot of letters goes inside another.
'ellas' is an anagram of 'alles'.
'ge' put within 'alles' is 'ALLEGES'.
Can you help me to learn more?
(Other definitions for alleges that I've seen before include "Holds" , "Asserts without proof" , "Declares to be the case without proof" , "Claims" , "States without proof" .)