Missile put up by eastern business (5)
I believe the answer is:
trade
'business' is the definition.
(trade is a kind of business)
'missile put up by eastern' is the wordplay.
'missile' becomes 'dart' (dart is a kind of missile).
'put up' says the letters should be written backwards.
'by eastern' becomes 'e' (I am not sure about the 'by' bit.).
'dart' back-to-front is 'trad'.
'trad'+'e'='TRADE'
Can you help me to learn more?
(Other definitions for trade that I've seen before include "Barter or swap" , "Transaction" , "Deal commercially" , "Business - (kind of) wind" , "Personal occupation" .)