Boring medic with information on large fish (8)

'boring' is the definition.
(I know that boring can be written as drilling)

'medic with information on large fish' is the wordplay.
I cannot really understand how this works, but
'medic' could be 'dr' (doctor) and 'dr' is present in the answer.
'information' could be 'i' (common abbreviation for information) and 'i' is found within the answer.
'large' could be 'l' (eg in clothes sizes) and 'l' is found in the answer.
'fish' could be 'ling' (ling is a kind of fish) and 'ling' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?