It prevents rocky ground becoming really stony (7-8)
I believe the answer is:
poverty-stricken
'really stony' is the definition.
(I've seen this before)
'it prevents rocky ground' is the wordplay.
'ground' indicates an anagram ('grind' the letters into a new form).
'it'+'prevents'+'rocky'='itpreventsrocky'
'itpreventsrocky' with letters rearranged gives 'POVERTY-STRICKEN'.
'becoming' is the link.
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