On the house (4)
'on the house' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gratis that I've seen before include "Without payment" , "Free of charge" , "Free, at no cost" , "Without charge" , "Free, costs nothing" .)
'on the house' is the definition.
(something on the house is given away free)
This is all the clue.
(Other definitions for free that I've seen before include "Release; gratis" , "As cheap as can be!" , "Release - without charge" , "Lavish" , "Complimentary" .)