Uncertainty of meaning (9)
I believe the answer is:
ambiguity
'uncertainty of meaning' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ambiguity that I've seen before include "Lack of a single meaning" , "Uncertainty of meaning" , "Equivocal expression" , "Something open to differing interpretations" , "Double meaning" .)