Bird of prey began early ascent, gliding low elegantly (5)
I believe the answer is:
eagle
'bird of prey' is the definition.
(eagle is a kind of bird of prey)
'began early ascent gliding low elegantly' is the wordplay.
'began' says to take the initial letters (I've seen 'begin' mean this).
The first letters of 'early ascent gliding low elegantly' is 'EAGLE'.
(Other definitions for eagle that I've seen before include "might one be bald?" , "Aglee (anag.)" , "experts are putting more than albatross?" , "standard for the military is seen" , "Old comic" .)