Philosophy of returning praise is mocked at first (7)
I believe the answer is:
dualism
'philosophy' is the definition.
(dualism is a kind of philosophy)
'returning praise is mocked at first' is the wordplay.
'returning' says the letters should be written backwards.
'praise' becomes 'laud' (lauding is a kind of praising**).
'at first' indicates taking the first letters.
The first letter of 'mocked' is 'm'.
'laud' written backwards gives 'dual'.
'dual'+'is'+'m'='DUALISM'
'of' is the link.
(Other definitions for dualism that I've seen before include "Division into two opposed aspects" , "Eg, what Yin and Yang represent" , "Belief in two basic entities" .)