Pineapple rings in syrup (9)
I believe the answer is:
grenadine
'syrup' is the definition.
(grenadine is a kind of syrup)
'pineapple rings in' is the wordplay.
'pineapple' becomes 'grenade' (I've seen this before).
'rings' means one lot of letters goes inside another.
'grenade' going around 'in' is 'GRENADINE'.
(Other definitions for grenadine that I've seen before include "Syrup - endearing (anag)" , "material" , "Cordial made from pomegranates" , "Pomegranate cordial" , "Pomegranate juice syrup" .)