Start to grasp socially acceptable English dance (7)
I believe the answer is:
beguine
'dance' is the definition.
(I know that beguine is a type of ballroom dance)
'start to grasp socially acceptable english' is the wordplay.
'start' becomes 'begin' (synonyms).
'to grasp' is an insertion indicator.
'socially acceptable' becomes 'u'.
'english' becomes 'e' (abbreviation).
'begin' placed around 'u' is 'beguin'.
'beguin'+'e'='BEGUINE'
(Other definitions for beguine that I've seen before include "Dance of French West Indian origin" , "Cole Porter song: 'Begin the .......'" , "French West Indian 20" .)