Porter, say, must keep a dray and available fare (1,2,5)
I believe the answer is:
a la carte
'available fare' is the definition.
(fare or food available on a menu)
'porter say must keep a dray' is the wordplay.
'porter say' becomes 'ale' (porter is a kind of ale).
'must keep' is an insertion indicator.
'dray' becomes 'cart' (I've seen this in another clue).
'a'+'cart'='acart'
'ale' enclosing 'acart' is 'A LA CARTE'.
'and' is the link.
(Other definitions for a la carte that I've seen before include "freedom to choose" , "Menu with items indiviually listed and priced" , "offering unrestricted choice" , "Unrestricted in restaurant choice" , "The posh menu, pick what you like" .)