Energy in giant mammals perverted sexual attraction (6,9)
I believe the answer is:
animal magnetism
'sexual attraction' is the definition.
(I've seen this before)
'energy in giant mammals perverted' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'perverted' is an anagram indicator.
'e'+'in'+'giant'+'mammals'='eingiantmammals'
'eingiantmammals' with letters rearranged gives 'ANIMAL MAGNETISM'.
(Other definitions for animal magnetism that I've seen before include "Zoo attraction" , "Polar bears might exert such a pull" , "Physical attractiveness" , "Sexual attraction" .)