Hide set when generator's lead turns cold (7)
I believe the answer is:
conceal
'hide' is the definition.
(synonyms)
'set when generator's lead turns cold' is the wordplay.
I cannot really see how this works, but
'when' could be 'once' (synonyms) and 'once' is located in the answer.
'cold' could be 'c' (eg on taps) and 'c' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for conceal that I've seen before include "'Hide, keep secret (7)'" , "Hide, cover" , "Place out of sight" , "hush up!" , "Keep out of sight" .)