Rich, posh lass almost organised educational grant (11)
I believe the answer is:
scholarship
'educational grant' is the definition.
(I've seen this before)
'rich posh lass almost organised' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'organised' is an anagram indicator.
'rich'+'posh'+'lass'='richposhlass'
'richposhlass' with its last letter taken off is 'richposhlas'.
'richposhlas' is an anagram of 'SCHOLARSHIP'.
(Other definitions for scholarship that I've seen before include "(Award for) academic skill" , "Work of 6 [ACADEMIA]" , "(Grant awarded for) academic learning" , "Academic achievement" , "Student maintenance grant" .)