Vocal German bloke uncapped dirty cosmetic (4,3)

I believe the answer is:

hair oil

I'm a little stuck... Click here to teach me more about this clue!

'cosmetic' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?

'vocal german bloke uncapped dirty' is the wordplay.
'vocal german bloke' becomes 'hair' (I am not sure about this - if you are sure you should believe this answer much more).
'uncapped' means to remove the first letter.
'dirty' becomes 'soil' (synonyms).
'soil' with its first letter taken away is 'oil'.
'hair'+'oil'='HAIR-OIL'

Can you help me to learn more?

(Other definitions for hair oil that I've seen before include "Toiletry used on the head" , "Brilliantine, for example" .)

I've seen this clue in the Sydney Morning Herald.

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