Nile made up Egypt's back passage (5)
I believe the answer is:
inlet
'passage' is the definition.
(I've seen this before)
'nile made up egypt's back' is the wordplay.
'made up' indicates an anagram.
'back' suggests the final letters (the letter at the back).
The final letter of 'egypt' is 't'.
'nile' is an anagram of 'inle'.
'inle'+'t'='INLET'
(Other definitions for inlet that I've seen before include "Fjord" , "Entry; arm of the sea" , "bit of a lake here?" , "Opening - passage" , "An entrance or opening" .)