Incisive, a new leader of team by ditch (9)
I believe the answer is:
trenchant
'incisive' is the definition.
(I've seen this before)
'a new leader of team by ditch' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'leader of' suggests taking the first letters.
'by' says to put letters next to each other.
'ditch' becomes 'trench' (synonyms).
The initial letter of 'team' is 't'.
'a'+'n'+'t'='ant'
'ant' put after 'trench' is 'TRENCHANT'.
(Other definitions for trenchant that I've seen before include "Incisive in style" , "Distinctly defined" , "Keen" , "Sharp" , "Acerbic" .)