Extremely significant widespread conflict (6)
I believe the answer is:
strife
'conflict' is the definition.
(I know that strife is a type of conflict)
'extremely significant widespread' is the wordplay.
'extremely' suggests removing the centre (only the extremes of the word are used).
'widespread' becomes 'rife' (I've seen this in another clue).
'significant' with its centre removed is 'st'.
'st'+'rife'='STRIFE'
(Other definitions for strife that I've seen before include "Lack of harmony" , "Bitter disagreement" , "Trouble and conflict" , "Struggle" , "Conflict, dispute" .)