I could google what the first part means yet I can't see what "about it" adds to it. Does the expression mean the same without the last part?
whiff of something (sg) TDF an idiom
- . Lit. the smell or odor of something. (*Typically: get ~; catch ~; have ~; take ~; give someone ~.)
Did you get a whiff of the turkey roasting? Yummy. I caught a whiff of something rather unpleasant in the attic. I think there is a dead mouse up there.
- . Fig. a bit of knowledge of something. (*Typically: get ~; catch ~; give someone ~.)
The boss got a whiff of problems in the accounting department. No one will get a whiff of your crime with the police. I'll see to that.
'About it' is not necessarily ... necessary. It depends on the context and grammatical construction you choose. The necessary is 'sg'.
"about" means "in the area of", "nearby", as per the second definition of this entry.
"whiff" is smell or odor, so to say something "has a whiff about it" means there is a smell in the nearby area. It's slightly less definite than to say 'something has a whiff", which means that the whiff is definitely a property of the object, but means that the whiff is nearby and is probably associated with the object.