It could drive many people mad missing out on promotion, challenging in vain (7)
I believe the answer is:
minivan
'it could drive' is the definition.
I know nothing about this answer so I can't tell whether this works.
'many people mad missing out on promotion challenging in vain' is the wordplay.
I cannot quite understand how this works, but
'many' could be 'm' (Roman numeral for a thousand) and 'm' is located in the answer.
'in' is found in the answer.
an anagram of 'vain' is 'ivan' which is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for minivan that I've seen before include "transporter" , "vehicle" , "Transport" .)