Trailblazers -- one found in jetties (8)
I believe the answer is:
pioneers
'trailblazers' is the definition.
(I've seen this before)
'one found in jetties' is the wordplay.
'found in' means one lot of letters goes inside another.
'jetties' becomes 'piers' (I've seen this before).
'one' placed into 'piers' is 'PIONEERS'.
(Other definitions for pioneers that I've seen before include "Innovators" , "First settlers in a new territory" , "They open up new territories" , "Ground-breakers, trail-blazers" .)