Stretch out at first in elegant manoeuvring (8)
I believe the answer is:
elongate
'stretch' is the definition.
(to elongate is to stretch out)
'out at first in elegant manoeuvring' is the wordplay.
'at first' suggests taking the first letters.
'in' is an insertion indicator.
'manoeuvring' indicates an anagram.
The initial letter of 'out' is 'o'.
'elegant' anagrammed gives 'elngate'.
'o' inserted into 'elngate' is 'ELONGATE'.
(Other definitions for elongate that I've seen before include "Open out" , "Draw out" , "Stretch lengthways" , "Stretch, pull" , "Make longer" .)