Shade indefinite number, sort by value (4,4)
I believe the answer is:
navy blue
'shade' is the definition.
(shade of blue)
'indefinite number sort by value' is the wordplay.
'indefinite number' becomes 'n' (n can represent any number).
'sort' is an anagram indicator.
'by'+'value'='byvalue'
'byvalue' is an anagram of 'avyblue'.
'n'+'avyblue'='NAVY-BLUE'
(Other definitions for navy blue that I've seen before include "Senior Service shade" , "Colour darker than royal" , "Dark shade, worn by mariners?" , "Shade - venal buy (anag)" , "Armed service shade?" .)