Suspect calls with promise (7)
I believe the answer is:
dubious
'suspect' is the definition.
(I've seen this before)
'calls with promise' is the wordplay.
'calls' becomes 'dubs' (dubbing is a kind of calling).
'with' is an insertion indicator.
'promise' becomes 'iou' (I owe you, a promise to pay a debt).
'dubs' enclosing 'iou' is 'DUBIOUS'.
(Other definitions for dubious that I've seen before include "Ambiguous or suspect" , "Open to question" , "Open to suspicion" , "Morally suspect" , "Of questionable value" .)