Speed effortlessly through part, not needing this? (6)
I believe the answer is:
prompt
'not needing this?' is the definition.
The definition suggests a singular noun which matches the answer.
'speed effortlessly through part' is the wordplay.
'speed effortlessly' becomes 'romp'.
'through' means one lot of letters goes inside another (I've seen this in other clues).
'part' becomes 'pt' (I've seen this in other clues**).
'romp' put inside 'pt' is 'PROMPT'.
(Other definitions for prompt that I've seen before include "Cue given to actor" , "Speedy - help for forgetful actor" , "On the dot" , "Urge - done without delay" , "Arriving on time" .)