Building a car with child in charge shows trendy affectation (7,4)
I believe the answer is:
radical chic
'affectation' is the definition.
(I know that radical chic is a type of affectation)
'building a car with child in charge' is the wordplay.
'building' is an anagram indicator.
'with' means one lot of letters go next to another.
'in charge' becomes 'ic' (abbreviation for 'in charge').
'a'+'car'='acar'
'acar' put after 'child' is 'childacar'.
'childacar' is an anagram of 'radicalch'.
'radicalch'+'ic'='RADICAL CHIC'
'shows trendy' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for radical chic that I've seen before include "Fashionable left-wing style" , "Fashionable left-leaning style" , "Fashionable extremism" .)