Beach borders start of terribly unproductive land (3-5)

I believe the answer is:

set-aside

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'unproductive land' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?

'beach borders start of terribly' is the wordplay.
'beach' becomes 'seaside' (synonyms).
'borders' indicates putting letters inside (inserted letters are bordered by others).
'start of' indicates taking the first letters.
The initial letter of 'terribly' is 't'.
'seaside' going around 't' is 'SET-ASIDE'.

Can you help me to learn more?

I've seen this clue in The Independent.

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