Tricky cut into poor ground that's rocky (7)
I believe the answer is:
outcrop
'that's rocky' is the definition.
(a rocky formation)
'tricky cut into poor ground' is the wordplay.
'tricky' indicates anagramming the letters.
'into' indicates putting letters inside.
'ground' indicates anagramming the letters ('grind' the letters into a new form).
'cut' is an anagram of 'utc'.
'poor' with letters rearranged gives 'orop'.
'utc' placed within 'orop' is 'OUTCROP'.
(Other definitions for outcrop that I've seen before include "Sudden emergence" , "Surface eruption of rock" , "Not suitable" , "Part of a rock formation above the surface" , "Rocks projecting from ground" .)