Is able to get led astray by a light (6)
I believe the answer is:
candle
'a light' is the definition.
(candle is a kind of light)
'is able to get led astray' is the wordplay.
'is able to' becomes 'can' (if you can do something you are able to do it).
'get' is an insertion indicator.
'astray' indicates anagramming the letters.
'led' anagrammed gives 'dle'.
'can' put into 'dle' is 'CANDLE'.
'by' is the link.
(Other definitions for candle that I've seen before include "that's useful if power's cut" , "Lanced (anag)" , "Wax cylinder" , "Wax 21 ac source" , "Maeve Binchy novel 'Light a Penny ......'" .)