Possibly hard border? (5)

I believe the answer is:

hedge

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'possibly hard border?' is the definition.
'hedge' can be an answer for 'border?' (I have seen 'Border of vegetation ' mean 'hedge' so perhaps 'border' could also mean 'hedge'). I am unsure of the 'possibly hard' bit.

'hard border?' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'border?' becomes 'edge' (synonyms).
'h'+'edge'='HEDGE'

Can you help me to learn more?

(Other definitions for hedge that I've seen before include "Qualify by conditions; boundary of bushes" , "Be cautious" , "Bushy boundary" , "Windbreak" , "Row of bushes" .)

I've seen this clue in The Telegraph.

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