Examines nail that is beginning to split (7)
I believe the answer is:
studies
'examines' is the definition.
('study' can be a synonym of 'examine')
'nail that is beginning to split' is the wordplay.
'nail' becomes 'stud' (I've seen this before).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'beginning to' says to take the initial letters.
The first letter of 'split' is 's'.
'stud'+'ie'+'s'='STUDIES'
(Other definitions for studies that I've seen before include "Scrutinises" , "Closely inspects; rooms" , "Applies the mind to learning" , "Work done to acquire learning" , "lessons" .)