Working at loan without a key (6)
I believe the answer is:
atonal
'without a key' is the definition.
(I've seen this before)
'working at loan' is the wordplay.
'working' is an anagram indicator.
'at'+'loan'='atloan'
'atloan' anagrammed gives 'ATONAL'.
(Other definitions for atonal that I've seen before include "(Of music) without key" , "(Of music) not in any key or mode" , "(Of music) lacking key" , "Keyless" , "Unaccented" .)