Blue put on a green space, which is random (8)
I believe the answer is:
aleatory
'is random' is the definition.
(thesaurus)
'blue put on a green space' is the wordplay.
'blue' becomes 'tory' (I've seen this in other clues).
'put on' is a charade indicator (letters next to each other).
'green space' becomes 'lea' (type of field).
'a'+'lea'='alea'
'tory' after 'alea' is 'ALEATORY'.
'which' is the link.
(Other definitions for aleatory that I've seen before include "depending on chance" , "dependent on chance" .)