Cooker successfully installed on second occasion? (5)
I believe the answer is:
again
'on second occasion?' is the definition.
'cooker successfully installed' is the wordplay.
'cooker' becomes 'aga' (I've seen this before).
'successfully installed' becomes 'in' (put or located in).
'aga'+'in'='AGAIN'
(Other definitions for again that I've seen before include "'Another time, once more (5)'" , "return" , "Next time" , "10 10 [AGAIN" , "Not for the first time" .)