Does it get narrower as it burns? (5)
I believe the answer is:
taper
'does it get narrower' is the definition.
I can't tell whether this definition defines the answer.
'it burns?' is the wordplay.
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'burns?' becomes 'aper' (I am not sure about this - if you are sure you should believe this answer much more).
't'+'aper'='TAPER'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for taper that I've seen before include "Get more narrow" , "See the light" , "Become thinner towards one end" , "Spill - become narrower towards one end" , "One making recording" .)