Potato (a lot, mashed) and a sausage (9)
I believe the answer is:
chipolata
'sausage' is the definition.
(I know that chipolata is a type of sausage)
'potato a lot mashed and a' is the wordplay.
'potato' becomes 'chip' (I have seen 'Fried potato ' mean 'chip' so perhaps 'potato' could also mean 'chip').
'mashed' is an anagram indicator.
'and' says to put letters next to each other.
'a'+'lot'='alot'
'alot' with letters rearranged gives 'olat'.
'chip'+'olat'+'a'='CHIPOLATA'
(Other definitions for chipolata that I've seen before include "banger" , "Small thin sausage" , "Party snack" , "Type of sausage" .)