Ensures that you know they’re on the house (8)
I believe the answer is:
presents
'ensures' is the definition.
The answer and definition can be both to do with communicating as well as being verbs in their -s form.
Maybe there's an association between them I don't understand?
'you know they're on the house' is the wordplay.
I cannot quite understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is present in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This explanation may well be incorrect...
'that' acts as a link.
Can you help me to learn more?
(Other definitions for presents that I've seen before include "Offerings" , "Hands over the gifts" , "donations" , "special things at Christmas?" , "tips" .)