Fruit-tree one of five arriving together with Civil Engineer (6)
I believe the answer is:
quince
'fruit-tree' is the definition.
(quince is a type of fruit tree)
'one of five arriving together with civil engineer' is the wordplay.
'one of five arriving together' becomes 'quin' (short for quintuplet).
'with' says to put letters next to each other.
'civil engineer' becomes 'ce'.
'quin'+'ce'='QUINCE'
(Other definitions for quince that I've seen before include "Preserve material" , "Fruity" , "Acid pear-shaped fruit used in preserves" , "part-time Athenian dramatist" , "Chips" .)