Strongly criticise a course of action taken by team's leader (6)
I believe the answer is:
attack
'strongly criticise' is the definition.
(I've seen this before)
'a course of action taken by team's leader' is the wordplay.
'course of action' becomes 'tack' (I've seen this before).
'taken by' means one lot of letters go next to another.
'leader' indicates taking the first letters.
The initial letter of 'teams' is 't'.
'tack' after 't' is 'ttack'.
'a'+'ttack'='ATTACK'
(Other definitions for attack that I've seen before include "Pitch into" , "An assault or onslaught" , "Strike" , "storm" , "Brownish pigment" .)