Set fire to some long speech (6)
I believe the answer is:
litany
'long speech' is the definition.
'litany' can be an answer for 'speech' (litany is a kind of speech). I'm not certain of the 'long' bit.
'set fire to some' is the wordplay.
'set fire' becomes 'lit' (I've seen this in other clues).
'to some' becomes 'any' ('any' can be similar in meaning to 'some').
'lit'+'any'='LITANY'
Can you help me to learn more?
(Other definitions for litany that I've seen before include "religious text" , "long address" , "Tedious series (of complaints)" , "Long and tedious series" , "Prayer of invocation to the saints" .)