Thanks for each slender light (5)
I believe the answer is:
'slender light' is the definition.
'taper' can be an answer for 'light' (taper is a kind of light). I'm not sure about the 'slender' bit.
'thanks for each' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'for each' becomes 'per' (per person).
Can you help me to learn more?
(Other definitions for taper that I've seen before include "Wax light; narrow" , "Give a point" , "He records" , "Thin progressively" , "Gradually become thinner" .)