In partnership, weed out some fiddlers (6)
I believe the answer is:
wedded
'in partnership' is the definition.
(thesaurus)
'weed out some fiddlers' is the wordplay.
'out' is an insertion indicator.
'some fiddlers' becomes 'dd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'weed' enclosing 'dd' is 'WEDDED'.
Can you help me to learn more?
(Other definitions for wedded that I've seen before include "with wife" , "Committed" , "This bliss is of the married kind" , "Closely joined" , "This bliss is for married couples" .)