Take over the odd set of pet newts (4)
I believe the answer is:
efts
'newts' is the definition.
(eft is a kind of newt)
'take over the odd set of pet' is the wordplay.
'take over' says the letters should be written in reverse (I've seen 'taken over' mean this).
'the odd' indicates alternate letters.
'set'+'of'+'pet'='setofpet'
The alternating letters of 'setofpet' are 'stfe'.
'stfe' in reverse letter order is 'EFTS'.
(Other definitions for efts that I've seen before include "Old lizards" , "Baby newts" , "Amphibians" , "Kind of newts" .)