The domineering mother, fluster badly (9)
I believe the answer is:
masterful
'the domineering' is the definition.
(thesaurus)
'mother fluster badly' is the wordplay.
'mother' becomes 'ma' (ma is a kind of mother).
'badly' indicates anagramming the letters.
'fluster' is an anagram of 'sterful'.
'ma'+'sterful'='MASTERFUL'
(Other definitions for masterful that I've seen before include "Imperious" , "Authoritative" , "expert" , "overbearing" , "Domineering" .)