Maintain strict standards, as shown by this graph unit prepared (3,1,5,4)
I believe the answer is:
run a tight ship
'maintain strict standards' is the definition.
(to run a tight ship is to insist on high standards)
'shown by this graph unit prepared' is the wordplay.
'shown by' is a charade indicator (letters next to each other).
'prepared' indicates an anagram.
'this'+'graph'='thisgraph'
'thisgraph' next to 'unit' is 'thisgraphunit'.
'thisgraphunit' with letters rearranged gives 'RUN A TIGHT SHIP'.
'as' acts as a link.
(Other definitions for run a tight ship that I've seen before include "Enforce discipline" , "maintain discipline" , "Exert discipline in organisation" , "Be in control of an efficient organisation" , "Be strict in managing an organisation" .)