Works hard to get good service at empty tearooms (6)
I believe the answer is:
Here is my best explanation:
'works hard' is the definition.
(I've seen this before)
'good service at empty tearooms' is the wordplay.
'good' becomes 'g' (abbreviation).
'service' becomes 'raf' (**).
'at' means one lot of letters go next to another.
'empty' means to remove the middle letters.
'tearooms' with its middle taken out is 'ts'.
'to get' is the link.
(Other definitions for grafts that I've seen before include "Transplants", "Shoots from one plant fixed into another", "Works hard; transplants", "Splices or joins plant shoots together" and "Tree implants or corrupt business practices".)