Caught Pinter's first words? They're usually spiky (5)
I believe the answer is:
cacti
'they're usually spiky' is the definition.
(cacti are usually spiky)
'caught pinter's first words?' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'pinter's first words?' becomes 'ActI' (start of a play - Harold Pinter was a playwright).
'c'+'acti'='CACTI'
(Other definitions for cacti that I've seen before include "Spiny desert plants" , "They're decidedly prickly" , "Spiky desert plants in plural" , "they shoot in the desert" , "flowers" .)