Dodgy moment, not the first (4)
I believe the answer is:
Here is my best explanation:
'dodgy' is the definition.
(I've seen this before)
'moment not the first' is the subsidiary indication.
'moment' becomes 'jiffy' (I've seen this before).
'not the first' means to remove the first letter.
'jiffy' with its initial letter taken off is 'iffy'.
(Other definitions for iffy that I've seen before include "Risky", "Questionable (inf)", "Colloquially uncertain or doubtful", "Not certain, doubtful", "Informally dubious or uncertain", "Uncertain (colloq.)", "not kosher", "Doubtful (colloq.)", "Sixth (RU) Nation" and "Doubtful, not definite".)