Sailors in the shade (4)
I believe the answer is:
navy
I believe this clue is a double definition.
'sailors' is the first definition.
(group of sailors)
'the shade' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for navy that I've seen before include "Armed force" , "Blue - ships and seamen" , "Ships-of-war" , "Senior service" , "Shade of the marine forces" .)