Unusually posh gear brought back by large retail assistant (8)
I believe the answer is:
shopgirl
'retail assistant' is the definition.
The definition suggests a singular noun which matches the answer.
'unusually posh gear brought back by large' is the wordplay.
'unusually' is an anagram indicator.
'gear' becomes 'rig' (rig is a kind of gear).
'brought back' says the letters should be written backwards.
'by' says to put letters next to each other.
'large' becomes 'L' (eg in clothes sizes).
'rig' backwards is 'gir'.
'posh' with letters rearranged gives 'shop'.
'shop'+'gir'+'l'='SHOPGIRL'
Can you help me to learn more?
(Another definition for shopgirl that I've seen is " Retail employee".)