Pressure absorbed by land reptile (8)
I believe the answer is:
terrapin
'reptile' is the definition.
(I know that Testudinata parent taxon reptile)
'pressure absorbed by land' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'absorbed by' is an insertion indicator.
'land' becomes 'terrain' (terrain is land or territory).
'p' placed inside 'terrain' is 'TERRAPIN'.
(Other definitions for terrapin that I've seen before include "Small freshwater turtle" , "edible, freshwater reptile" , "A reptile; a printer (anag.)" , "Small species of turtle" , "Web-footed turtle" .)