Protective ring German field marshal left out in posh car (7)
I believe the answer is:
grommet
'posh car' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'protective ring german field marshal left out' is the wordplay.
'protective' becomes 'gt' (I can't justify this - if you can you should give a lot more credence to this answer).
'ring' means one lot of letters goes inside another.
'german field marshal' becomes 'rommel' (I've seen this before).
'left' becomes 'l' (common abbreviation).
'out' suggests deleting specific letters.
'rommel' with 'l' removed is 'romme'.
'gt' going around 'romme' is 'GROMMET'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for grommet that I've seen before include "Ring shaped to line a small hole" , "Tube passed through eardrum to drain it" , "Eyelet's metal ring" , "Metal ring for lining a small hole" , "Washer; eyelet" .)