Annoyed as new water heater, failing to start, died (7)
I believe the answer is:
nettled
'annoyed' is the definition.
(I know that annoyed can be written as nettled)
'new water heater failing to start died' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'water heater' becomes 'kettle' (I've seen this in another clue).
'failing to start' means to remove the first letter.
'died' becomes 'd' (abbreviation next to the year of someone's death).
'kettle' with its initial letter removed is 'ettle'.
'n'+'ettle'+'d'='NETTLED'
'as' acts as a link.
(Other definitions for nettled that I've seen before include "Annoyed, irritated" , "becomes annoyed" , "Annoyed as by stinging plant" , "Irritated as by stinging plant" , "Stung!" .)