The kind that's less than forty pesos (4)
I believe the answer is:
type
'the kind' is the definition.
(type is a kind of kind)
'less than forty pesos' is the wordplay.
'less' indicates a hidden word (the clue less some of the letters in it).
'TYPE' is hidden within 'than forty pesos'.
'that's' is the link.
(Other definitions for type that I've seen before include "Kind - kind of writing" , "Class, kind or printed characters" , "Thing or person of a specified kind" , "Class or group of a particular class" , "Courier for example" .)