Small fish sandwiches I polish off with large cordial (8)
I believe the answer is:
friendly
'cordial' is the definition.
(similar in meaning)
'small fish sandwiches i polish off with large' is the wordplay.
'small fish' becomes 'fry' (I've seen this in another clue).
'sandwiches' indicates putting letters inside (to sandwich is to block something in).
'polish off' becomes 'end' (polish off can mean to finish something).
'with' means one lot of letters go next to another.
'large' becomes 'L' (eg in clothes sizes).
'i'+'end'+'l'='iendl'
'fry' enclosing 'iendl' is 'FRIENDLY'.
(Other definitions for friendly that I've seen before include "such a society" , "Amiable" , "Kind, pleasant" , "Well-disposed" , "Amicable, favourably disposed" .)