In taking just seconds, lawyer advising her client initially to enter dock reveals incompetence (10)
I believe the answer is:
inadequacy
'incompetence' is the definition.
(thesaurus)
'in taking just' is the wordplay.
'taking' says to put letters next to each other.
'just' becomes 'adequacy' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in'+'adequacy'='INADEQUACY'
'seconds lawyer advising her client initially to enter dock reveals' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Another definition for inadequacy that I've seen is " Failing".)