Bridge partners terrible (6)
I believe the answer is:
weevil
'bridge' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'partners terrible' is the wordplay.
'partners' becomes 'we' (West and East are partners in the game bridge).
'terrible' becomes 'evil' (I can't explain this - if you can you should give a lot more credence to this answer).
'we'+'evil'='WEEVIL'
Can you help me to learn more?
(Other definitions for weevil that I've seen before include "Type of beetle that feeds of stored grain etc" , "Insect that feeds on plant products" , "Small beetle that feeds on plants" , "Small beetle with a long snout" , "little creature" .)