Cafe's penultimate potato dish; one's left in reserve (5)
I believe the answer is:
frost
'reserve' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'cafe's penultimate potato dish one's left' is the wordplay.
'cafe's penultimate' becomes 'f' (I can't explain this - if you can you should believe this answer much more).
'potato dish' becomes 'rosti' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'left' suggests deleting specific letters (some letters have left).
'rosti' with 'i' taken out is 'rost'.
'f'+'rost'='FROST'
'in' is the link.
Can you help me to learn more?
(Other definitions for frost that I've seen before include "Ice forming in cold weather" , "Frozen dew" , "Coldness of manner" , "Frozen deposit" , "RD Wingfield's detective" .)