American embraces endlessly resilient old scientist (10)
I believe the answer is:
astronomer
'scientist' is the definition.
(astronomer is a kind of scientist)
'american embraces endlessly resilient old' is the wordplay.
'american' becomes 'amer' (rare abbreviation**).
'embraces' is an insertion indicator.
'endlessly' means to remove the last letter.
'resilient' becomes 'strong' (I've seen this before).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'strong' with its final letter taken off is 'stron'.
'stron'+'o'='strono'
'amer' placed around 'strono' is 'ASTRONOMER'.
(Other definitions for astronomer that I've seen before include "Moon starer (anag.)" , "One studying the universe" , "Sky-at-night observer" , "Star-watcher" , "Stargazer" .)