Regarded as a bit of a key man (4)
I believe the answer is:
eyed
'regarded' is the definition.
(I've seen this in another clue)
'a bit of a key man' is the wordplay.
I cannot really understand how this works, but
'key' could be 'd' (musical key) and 'd' is present in the answer.
The remaining letters 'eye' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'as' is the link.
Can you help me to learn more?
(Other definitions for eyed that I've seen before include "Ogled" , "Spotted" , "Watched, looked at" , "Looked at, warily perhaps" , "Watched warily" .)