11 or 12 February? (4)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Double definition. Reference to 11d PLUS ONE: date = someone that you pair up with for a specific occasion (or more than one). Or a definition by example, indicated by the question mark: 12 February is an example of a date (and I’m not aware that it has any particular significance for this puzzle).