Call promissory notes questionable (7)
I believe the answer is:
dubious
'questionable' is the definition.
(similar in meaning)
'call promissory notes' is the wordplay.
'call' becomes 'dub' (both can mean to name).
'promissory notes' becomes 'ious' (IOU is an example).
'dub'+'ious'='DUBIOUS'
(Other definitions for dubious that I've seen before include "Of questionable value" , "Open to suspicion" , "Uncertain - suspect" , "Doubtful, uncertain" , "Doubtful, not convinced" .)