Great but less than devastating (4)
I believe the answer is:
vast
'great' is the definition.
(I've seen this before)
'less than devastating' is the wordplay.
'less' says the answer is hidden in the clue (the clue less some of the letters in it).
'VAST' is hidden within 'than devastating'.
'but' is the link.
(Other definitions for vast that I've seen before include "Boundless" , "Of very great extent" , "Huge, enormous" , "'Huge, immense (4)'" , "Unusually great" .)