A sovereign I preserve in instant coffee (9)
I believe the answer is:
americano
'coffee' is the definition.
(I've seen this before)
'a sovereign i preserve in instant' is the wordplay.
'sovereign' becomes 'er' (Abbreviation for Elizabeth Regina).
'preserve' becomes 'can' (canning is a kind of preserving).
'in' is an insertion indicator.
'instant' becomes 'mo'.
'er'+'i'+'can'='erican'
'erican' inserted into 'mo' is 'mericano'.
'a'+'mericano'='AMERICANO'
(Other definitions for americano that I've seen before include "Style of coffee" , "Espresso diluted with hot water" , "drink" .)