Underwear tight at first after manoeuvring legs in (7)
I believe the answer is:
singlet
'underwear' is the definition.
(I know that singlet is a type of undershirt)
'tight at first after manoeuvring legs in' is the wordplay.
'at first' indicates taking the first letters.
'after' means one lot of letters go next to another.
'manoeuvring' indicates anagramming the letters.
The first letter of 'tight' is 't'.
'legs'+'in'='legsin'
'legsin' is an anagram of 'single'.
't' put after 'single' is 'SINGLET'.
(Other definitions for singlet that I've seen before include "Tingles in vest" , "Underwear" , "One unaccompanied" , "top gear" , "underclothing" .)