Edgy UK native extremely tense crossing lake (7)
I believe the answer is:
brittle
'edgy' is the definition.
(brittle can mean edgy or anxious)
'uk native extremely tense crossing lake' is the wordplay.
'uk native' becomes 'brit' (short for Briton, someone from Britain).
'extremely' suggests removing the centre (only the extremes of the word are used).
'crossing' indicates putting letters inside (to cross can mean to go over or around).
'lake' becomes 'L' (geographical abbreviation).
'tense' with its middle taken out is 'te'.
'te' going around 'l' is 'tle'.
'brit'+'tle'='BRITTLE'
(Other definitions for brittle that I've seen before include "Hard but liable to break easily" , "Hard confectionery made with nuts" , "Easily cracked or snapped" , "Hard but easily broken" , "apt to snap" .)