Summarising at length, not taking sides (2,3)
I believe the answer is:
in all
'summarising' is the definition.
(I've seen this before)
'at length not taking sides' is the wordplay.
'at length' becomes 'finally' (synonyms).
'not taking sides' says to take the centre (the external or side letters are removed).
The central letters of 'finally' are 'IN ALL'.
(Other definitions for in all that I've seen before include "Altogether" , "totally" , "Taken together" , "Completely" , "without exception" .)