Eagle in uncontrolled descent (7)
I believe the answer is:
lineage
'descent' is the definition.
(I know that descent can be written as lineage)
'eagle in uncontrolled' is the wordplay.
'uncontrolled' is an anagram indicator.
'eagle'+'in'='eaglein'
'eaglein' anagrammed gives 'LINEAGE'.
(Other definitions for lineage that I've seen before include "Descent (from an ancestor)" , "Stock" , "Direct descent" , "The strain" , "Line of descendants of an ancestor" .)