Cereal from central Hampshire, in the past (4)
I believe the answer is:
sago
'cereal' is the definition.
(I've seen this before)
'central hampshire in the past' is the wordplay.
'central' indicates the central letters.
'in the past' becomes 'ago' ('ago' can be a synonym of 'in the past').
The central letter of 'hampshire' is 's'.
's'+'ago'='SAGO'
'from' acts as a link.
(Other definitions for sago that I've seen before include "Cereal, used in pudding" , "Edible powdery starch" , "dessert?" , "Type of milk pudding" , "Starchy foodstuff" .)