Beat up, turning stale, perhaps (7)
I believe the answer is:
pulsate
'beat' is the definition.
(I know that beat can be written as pulsate)
'up turning stale perhaps' is the wordplay.
'turning' says the letters should be written backwards.
'perhaps' indicates anagramming the letters.
'up' back-to-front is 'pu'.
'stale' is an anagram of 'lsate'.
'pu'+'lsate'='PULSATE'
(Other definitions for pulsate that I've seen before include "Expand and contract regularly" , "Produce a regular throbbing sensation" , "thrill" , "Throb regularly like heart" .)