Small sailors are celebrities (5)
I believe the answer is:
stars
'are celebrities' is the definition.
(star can mean a famous person)
'small sailors' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'sailors' becomes 'tars' (tar is a kind of sailor).
's'+'tars'='STARS'
(Other definitions for stars that I've seen before include "Leading actors" , "Leading performers (with stripes?)" , "Celestial bodies of hot gases" , "Heavenly bodies" , "''What is the ...? What is the ...? '' (Juno and the Paycock)" .)