Refuse to take about 100 in plane (6)
I believe the answer is:
reject
'refuse' is the definition.
('reject' can be a synonym of 'refuse')
'about 100 in plane' is the wordplay.
'about' becomes 're' (regarding**).
'r00' becomes 'c' ('C' can be a synonym of 'r00').
'in' means one lot of letters goes inside another.
'plane' becomes 'jet' (jet is a kind of plane).
'c' going within 'jet' is 'ject'.
're'+'ject'='REJECT'
'to take' acts as a link.
(Other definitions for reject that I've seen before include "Refuse to accept, send back" , "Decline" , "Throw out" , "Refuse to accept or react against" , "Turn away" .)