Crossword Genius

Shameful police officer sure to guzzle cider when working (13)

Ross

I believe the answer is:

discreditable

I'm a little stuck... Click here to teach me more about this clue!

'shameful' is the definition.
(I've seen this before)

'police officer sure to guzzle cider when working' is the wordplay.
I cannot quite see how this works, but
'police' could be 'dis' (detective inspectors or DIs) and 'dis' is found in the answer.
an anagram of 'cider' is 'credi' which is located in the answer.
The remaining letters 'table' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for discreditable that I've seen before include "Shameful" , "Tending to bring harm to a reputation" .)

I've seen this clue in The Telegraph.
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