Prickly shrub old comedy actor cut back (5)

I believe the answer is:

brier

I'm a little stuck... Click here to teach me more about this clue!

'prickly shrub' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for brier that I've seen before include "smoking pipe" , "Thorny bush like the wild rose" , "It may be smoked" , "plant" , "Prickly shrub" .)

I've seen this clue in The Telegraph.

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