Classy business graduate holding rook in dark place (5)
I believe the answer is:
umbra
'dark place' is the definition.
(I've seen this before)
'classy business graduate holding rook' is the wordplay.
'classy' becomes 'u' (U can mean upper class as in U- and non-U speech).
'business graduate' becomes 'MBA' (Master of Business Administration degree).
'holding' means one lot of letters goes inside another.
'rook' becomes 'R' (chess abbreviation).
'mba' placed around 'r' is 'mbra'.
'u'+'mbra'='UMBRA'
'in' acts as a link.
(Other definitions for umbra that I've seen before include "Rumba (anag.)" , "Deep shadow" , "Dark region" , "Shade, or ghost" , "Dark shadow cast by earth in eclipse" .)