Beat United -- last beaten during exercises (7)
I believe the answer is:
pulsate
'beat' is the definition.
(pulsating is a kind of beating)
'united last beaten during exercises' is the wordplay.
'united' becomes 'u' (**).
'beaten' indicates an anagram.
'during' is an insertion indicator.
'exercises' becomes 'pe'.
'last' with letters rearranged gives 'lsat'.
'u'+'lsat'='ulsat'
'ulsat' put into 'pe' is 'PULSATE'.
(Other definitions for pulsate that I've seen before include "thrill" , "Produce a regular throbbing sensation" , "Expand and contract regularly" , "Throb regularly like heart" .)