Like Nelson's tooth, with lack of metal filling? (9)
I believe the answer is:
monocular
'like nelson's' is the definition.
(Horatio Nelson ended up with only one eye)
'tooth with lack of metal filling?' is the wordplay.
'tooth' becomes 'molar' (molar is a kind of tooth).
'with' is an insertion indicator.
'lack of' becomes 'no' (lack of money is no money).
'metal filling?' becomes 'cu' (I can't explain this - if you can you should give a lot more credence to this answer).
'no'+'cu'='nocu'
'molar' going around 'nocu' is 'MONOCULAR'.
(Another definition for monocular that I've seen is " having limited vision".)