Idiot seeing service losing millions (3)
I believe the answer is:
ass
'idiot' is the definition.
(I've seen this before)
'service losing millions' is the wordplay.
'service' becomes 'mass' (I've seen this in other clues).
'losing' is a deletion indicator.
'millions' becomes 'm' (abbreviation).
'mass' with 'm' removed is 'ASS'.
'seeing' is the link.
(Other definitions for ass that I've seen before include "Pompous person" , "Trump's behind" , "Horse hybrid" , "Dolt" , "Blockhead" .)