Examine short fastener (4)
I believe the answer is:
stud
'fastener' is the definition.
(I've seen this before)
'examine short' is the wordplay.
'examine' becomes 'study' (synonyms).
'short' means to remove the last letter.
'study' with its last letter taken off is 'STUD'.
(Other definitions for stud that I've seen before include "Jewellery item; horse breeding establishment" , "Collar button or horse farm" , "Sex god" , "Virile man" , "Dot" .)