The limb used digital protection (7)
I believe the answer is:
thimble
'digital protection' is the definition.
(I've seen this before)
'the limb used' is the wordplay.
'used' indicates an anagram.
'the'+'limb'='thelimb'
'thelimb' with letters rearranged gives 'THIMBLE'.
(Other definitions for thimble that I've seen before include "one player conceals in game" , "Sewer's protector" , "Protection from a needle" , "Protective item for the tailor" , "Finger-guard" .)