Harshly criticise second strike (4)
I believe the answer is:
slam
'harshly criticise' is the definition.
'second strike' is the wordplay.
'second' becomes 's' (common abbreviation).
'strike' becomes 'lam' (to 'lam' means to hit hard).
's'+'lam'='SLAM'
(Other definitions for slam that I've seen before include "what needs a lot of tricks to succeed" , "Shut loudly and forcibly" , "Criticise - attack" , "Crash (door closed)" , "ambitious bid" .)