Car is no trouble in fourth gear - work that one out? (6)
I believe the answer is:
teaser
'car' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'no trouble in fourth gear work that one out?' is the wordplay.
'no trouble' becomes 'ease' (I've seen this before).
'in fourth gear work' becomes 'tr' (I am not sure about this - if you are sure you should believe this answer much more).
'that one out?' means one lot of letters goes inside another.
'ease' placed inside 'tr' is 'TEASER'.
'is' is the link.
Can you help me to learn more?
(Other definitions for teaser that I've seen before include "Difficult question" , "inducement" , "Puzzling question or gentle goader" , "One who pulls someone's leg" , "Introduction to arouse curiosity" .)