A detective group in Canberra starts to get bitter (6)
I believe the answer is:
acidic
'bitter' is the definition.
(I've seen this in another clue)
'a detective group in canberra starts to' is the wordplay.
'a detective group' becomes 'acid' (I can't explain this - if you can you should give a lot more credence to this answer).
'starts to' suggests taking the first letters.
The first letters of 'in canberra' is 'ic'.
'acid'+'ic'='ACIDIC'
'get' is the link.
Can you help me to learn more?
(Other definitions for acidic that I've seen before include "Vinegary" , "Cutting" , "Tart, sour" , "Tasting sharp or sour" , "scathing?" .)