Choose one graduate lecturer as the very best (7)
I believe the answer is:
optimal
'the very best' is the definition.
(I've seen this before)
'choose one graduate lecturer' is the wordplay.
'choose' becomes 'opt' (both can mean to pick something).
'one' becomes 'i' (Roman numeral).
'graduate' becomes 'MA' (abbreviation for Master of Arts).
'lecturer' becomes 'l' (abbreviation for lecturer).
'opt'+'i'+'ma'+'l'='OPTIMAL'
'as' is the link.
(Other definitions for optimal that I've seen before include "Most favouring" , "Plot aim (anag) - most favourable" , "top, surprisingly" , "Plot aim (anag) - best" , "Best or most favourable" .)