Building unsecured if I certified locks (7)
I believe the answer is:
edifice
'building' is the definition.
(synonyms)
'unsecured if i certified locks' is the wordplay.
'locks' says the answer is hidden in the clue (I've seen 'locking' mean this).
'EDIFICE' is hidden in the letters of 'unsecured if i certified'.
(Other definitions for edifice that I've seen before include "Monument" , "Grand building" , "Fine building" , "Permanent building" , "'Large, imposing building (7)'" .)