Check gold key and object (5)
I believe the answer is:
audit
'check' is the definition.
(an audit is an examination or check)
'gold key and object' is the wordplay.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'key' becomes 'd' (musical key).
'and' means one lot of letters go next to another.
'object' becomes 'it' (pronoun for an inanimate object).
'au'+'d'+'it'='AUDIT'
(Other definitions for audit that I've seen before include "Inspection of the account books" , "Examine account" , "Financial check" , "Inspection of a company's books" , "Stocktake" .)