Retreat gets demeaning somehow (13)
I believe the answer is:
disengagement
'retreat' is the definition.
(I've seen this before)
'gets demeaning somehow' is the wordplay.
'somehow' is an anagram indicator.
'gets'+'demeaning'='getsdemeaning'
'getsdemeaning' with letters rearranged gives 'DISENGAGEMENT'.
(Other definitions for disengagement that I've seen before include "lack of interest?" , "A separating, releasing" , "Retreat" , "Mutual withdrawal" .)