Kowtowed - lowering head with a fibrous beard (5)

'kowtowed lowering head' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives can occasionally define each other.

'with a fibrous beard' is the wordplay.
I cannot really understand how this works, but
'with' could be 'w' (abbreviation) and 'w' is present in the answer.
'a' could be 'an' and 'an' is located in the remaining letters.
The remaining letters 'ed' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?