Star sailor buckled under pressure (7)
I believe the answer is:
polaris
'star' is the definition.
(Polaris is an example)
'sailor buckled under pressure' is the wordplay.
'buckled' is an anagram indicator.
'under' says to put letters next to each other.
'pressure' becomes 'p' (abbreviation).
'sailor' is an anagram of 'olaris'.
'olaris' put after 'p' is 'POLARIS'.
(Other definitions for polaris that I've seen before include "one belonging in the heavens" , "North Star - missile" , "Star near the N pole of the heavens" , "Star useful for navigation" , "star (non-movie)" .)