It carries a few people without including one bighead! (7)
I believe the answer is:
minibus
'it carries a few people' is the definition.
The definition suggests a singular noun which matches the answer.
'without including one bighead' is the wordplay.
'without' becomes 'minus' (minus means without).
'including' means one lot of letters goes inside another.
'one' becomes 'I' (Roman numeral).
'bighead' becomes 'b' (the head letter of 'big').
'i'+'b'='ib'
'minus' placed around 'ib' is 'MINIBUS'.
Can you help me to learn more?
(Other definitions for minibus that I've seen before include "Small multi-seater vehicle" , "transport for children?" , "form of transport" , "Small coach" , "Vehicle for up to, say, 15 passengers" .)