Consider female ninny? (6)

I believe the answer is:
assess
'consider' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for assess that I've seen before include "Evaluate, estimate" , "Make estimate or appraisal of" , "Rate, evaluate" , "'Evaluate, appraise (6)'" , "Weigh up, estimate value" .)