Transport pilots in waterway linking delta and sierra (7)
I believe the answer is:
drivers
'transport pilots' is the definition.
'waterway linking delta and sierra' is the wordplay.
'waterway' becomes 'river' (I've seen this before).
'linking' indicates putting letters inside (the inserted material links two sets of letters).
'delta' becomes 'd' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' means one lot of letters go next to another.
'sierra' becomes 's' (phonetic alphabet: alpha, bravo, charlie etc.).
'd'+'s'='ds'
'river' placed within 'ds' is 'DRIVERS'.
'in' acts as a link.
(Other definitions for drivers that I've seen before include "What PC needs" , "Chauffeurs" , "Golf clubs" , "Motorists; clubs" , "Motoring" .)