Hard stone receiving instant cut (6)
I believe the answer is:
strict
'hard' is the definition.
(I've seen this before)
'stone receiving instant cut' is the wordplay.
'stone' becomes 'st' (abbreviation).
'receiving' means one lot of letters goes inside another.
'instant' becomes 'trice' (both can mean a short amount of time).
'cut' means to remove the last letter.
'trice' with its final letter taken away is 'tric'.
'st' enclosing 'tric' is 'STRICT'.
(Other definitions for strict that I've seen before include "Austere - rigid" , "Rigidly enforced" , "Demanding that rules are observed" , "Excessive pride" , "Stringent" .)