Sweet tablet swallowed by Kitty going the wrong way (8)
I believe the answer is:
lollipop
'sweet' is the definition.
(lollipop is a kind of sweet)
'tablet swallowed by kitty going the wrong way' is the wordplay.
'tablet' becomes 'pill' ('pill' can be a synonym of 'tablet').
'swallowed by' is an insertion indicator.
'kitty' becomes 'pool' ('pool' can be a synonym of 'kitty').
'going the wrong way' says the letters should be written backwards.
'pill' placed into 'pool' is 'popillol'.
'popillol' in reverse letter order is 'LOLLIPOP'.
(Other definitions for lollipop that I've seen before include "Boiled sweet" , "children love it" , "Ice confection" , "Sweetmeat" , "Sweet; popular work" .)