Stone work unit hiding old article stops here (4,5)
I believe the answer is:
pipe organ
'stops here' is the definition.
(a pipe organ has parts called stops)
'stone work unit hiding old article' is the wordplay.
'stone' becomes 'pip' (**).
'work unit' becomes 'erg' (erg is a kind of work unit).
'hiding' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'article' becomes 'an' (indefinite article).
'erg' placed around 'o' is 'eorg'.
'pip'+'eorg'+'an'='PIPE-ORGAN'
(Other definitions for pipe organ that I've seen before include "Musical instrument" , "Traditional church instrument" .)