Wellington took the boss inside (7)
I believe the answer is:
gumboot
'wellington' is the definition.
(I've seen this before)
'took the boss inside' is the wordplay.
'took' becomes 'got' ('get' can be a synonym of 'take').
'the boss' becomes 'umbo' (the boss on a shield).
'inside' means one lot of letters goes inside another.
'got' enclosing 'umbo' is 'GUMBOOT'.
(Other definitions for gumboot that I've seen before include "Wader" , "Wellington" , "Waterproof footwear" .)