Soothe pulse during recess (7)
I believe the answer is:
appease
'soothe' is the definition.
(I've seen this in another clue)
'pulse during recess' is the wordplay.
'pulse' becomes 'pea' (I've seen this before).
'during' means one lot of letters goes inside another.
'recess' becomes 'apse' (apse is a kind of recess).
'pea' put within 'apse' is 'APPEASE'.
(Other definitions for appease that I've seen before include "Pacify with concessions" , "Quiet" , "Satisfy demands by making concessions" , "To behave like Chamberlain" , "Placate (someone) with concessions" .)