Regarded as rich after one short day (4)
I believe the answer is:
eyed
'regarded' is the definition.
(I've seen this in other clues)
'rich after one short day' is the wordplay.
'rich after one' becomes 'eye' (I can't explain this - if you can you should give a lot more credence to this answer).
'short day' becomes 'd' (abbreviation for day; 'short' indicates a short form).
'eye'+'d'='EYED'
'as' is the link.
Can you help me to learn more?
(Other definitions for eyed that I've seen before include "Spotted" , "Watched, looked at" , "Watched with interest" , "Stared at" , "Closely observed" .)