Support pants on men deter grasping soprano (11)
I believe the answer is:
endorsement
'support' is the definition.
(I know that endorsement is a type of support)
'pants on men deter grasping soprano' is the wordplay.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'grasping' indicates putting letters inside (inserted letters are held or grasped).
'soprano' becomes 's' (musical abbreviation).
'on'+'men'+'deter'='onmendeter'
'onmendeter' is an anagram of 'endorement'.
'endorement' placed around 's' is 'ENDORSEMENT'.
(Other definitions for endorsement that I've seen before include "Note on a driving licence" , "unwelcome to offending motorists" , "okay?" , "Sanction, backing" , "Penalty appended to driving licence" .)