At Mach ten flying team initially bond (10)
I believe the answer is:
attachment
'bond' is the definition.
(I know that bond can be written as attachment)
'at mach ten flying team initially' is the wordplay.
'flying' is an anagram indicator (letters fly around into new positions).
'initially' suggests taking the first letters.
The first letter of 'team' is 't'.
'mach'+'ten'='machten'
'machten' with letters rearranged gives 'tachmen'.
'at'+'tachmen'+'t'='ATTACHMENT'
(Other definitions for attachment that I've seen before include "what might accompany 50 [EMAIL]" , "File with an email" , "Liking" , "Fondness" , "communicated via e-mail" .)