Middle gear learner driver engaged in frightful ride (5)
I believe the answer is:
idler
'middle gear' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'learner driver engaged in frightful ride' is the wordplay.
'learner driver' becomes 'l' (learner drivers have L-plates on their cars).
'engaged in' is an insertion indicator.
'frightful' is an anagram indicator (a frightful spelling).
'ride' with letters rearranged gives 'ider'.
'l' put into 'ider' is 'IDLER'.
Can you help me to learn more?
(Other definitions for idler that I've seen before include "Laggard" , "Layabout; Dr Johnson essay series" , "Layabout; ship crewman not on watch" , "Slow-cooked dish" , "Lollard" .)