One lying about securing international portfolio (7)
I believe the answer is:
Here is my best explanation:
'one lying about securing international portfolio' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'one' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
The remaining letters 'dosser' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for dossier that I've seen before include "Collection of documents on a subject", "Report", "Record", "file", "brief", "Papers containing detailed information about someone", "Set of papers", "Papers containing detailed information about a particular person", "Brief" and "File of documents".)