Premium bond computer (5)
I believe the answer is:
ernie
'premium bond computer' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ernie that I've seen before include "Wise, perhaps" , "--- Wise, comedian" , "Machine that produces the winning Premium Bond numbers" , "Bondsman" , "Eric Morecambe & - - Wise" .)