Sweet thing back in memorial centre (6)
I believe the answer is:
eclair
'sweet thing' is the definition.
(I've seen this before)
'back in memorial centre' is the wordplay.
'back' says the letters should be written in reverse.
'in' indicates the answer is hidden within the clue.
'rialce' can be found hidden inside 'memorial centre'.
'rialce' in reverse letter order is 'ECLAIR'.
(Other definitions for eclair that I've seen before include "comedian Jenny?" , "I clear off with thin chocolate cake" , "Cake, "long in shape but short in duration"" , "Lacier type of cake" , "Long cream puff" .)