Flexible power in restored pulse (6)
I believe the answer is:
supple
'flexible' is the definition.
(similar in meaning)
'power in restored pulse' is the wordplay.
'power' becomes 'p'.
'in' is an insertion indicator.
'restored' indicates an anagram (I've seen this in other clues).
'pulse' with letters rearranged gives 'suple'.
'p' put into 'suple' is 'SUPPLE'.
(Other definitions for supple that I've seen before include "Opposite of stiff" , "Flexible (body)" , "Mobile" , "Lissom" , "Pliant, flexible" .)