Robust door finally installed in workroom (6)
I believe the answer is:
sturdy
'robust' is the definition.
(similar in meaning)
'door finally installed in workroom' is the wordplay.
'finally' says to take the final letters.
'installed in' indicates putting letters inside.
'workroom' becomes 'study' (I've seen this before).
The final letter of 'door' is 'r'.
'r' placed within 'study' is 'STURDY'.
(Other definitions for sturdy that I've seen before include "Strong and sturdily built" , "Firmly constructed" , "Strong and stout" , "Well-built - strapping" , "Uncompromising" .)