In break, see lively dance (5)
I believe the answer is:
galop
'lively dance' is the definition.
(I've seen this in another clue)
'in break see' is the wordplay.
'in' indicates putting letters inside.
'break' becomes 'gap' (a gap is a break in something).
'see' becomes 'lo' (archaic exclamation meaning 'look!').
'gap' placed around 'lo' is 'GALOP'.
(Other definitions for galop that I've seen before include "dance music" , "Nineteenth-century dance" , "Couple dance" , "Lively ballroom dance" .)