One enthralled by cat maybe is maiden showing excessive devotion (7)
I believe the answer is:
pietism
'excessive devotion' is the definition.
(being overly pious)
'one enthralled by cat maybe is maiden' is the wordplay.
'one' becomes 'I' (Roman numeral).
'enthralled by' is an insertion indicator ('enthral' can mean 'capture').
'cat maybe' becomes 'piets' (I can't explain this - if you can you should give a lot more credence to this answer).
'is maiden' becomes 'm' (cricket abbreviation).
'i' going inside 'piets' is 'pietis'.
'pietis'+'m'='PIETISM'
'showing' acts as a link.
(Another definition for pietism that I've seen is " Hypocrisy".)