Whole area with two students (3)
I believe the answer is:
all
'whole' is the definition.
(I have seen 'The whole ' mean 'all' so perhaps 'whole' could also mean 'all')
'area with two students' is the wordplay.
'two students' means two substitutions for 'student'.
'area' becomes 'a' (maths abbreviation).
'with' means one lot of letters go next to another.
'student' becomes 'L' (as in L-plates for learner drivers).
'student' becomes 'l' (as in L-plates for learner drivers).
'a'+'l'+'l'='ALL'
(Other definitions for all that I've seen before include "Entire" , "Every single one" , "Straight garden path" , "and 18: 'Sing through -- --' (carol)" , "without exception" .)