Announced I would be kept under observation (4)
I believe the answer is:
eyed
'under observation' is the definition.
(I've seen this in another clue)
'announced i would' is the wordplay.
'announced' indicates a 'sounds like' (homophone) clue.
'i would' becomes 'I'd'.
'id' sounds like 'EYED'.
'be kept' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for eyed that I've seen before include "Vegetable" , "Looked at closely" , "Watched with interest" , "Looked at, warily perhaps" , "Watched warily" .)