I initially considered you hostile (3)
I believe the answer is:
icy
'hostile' is the definition.
(I've seen this before)
'i initially considered you' is the wordplay.
'initially' says to take the initial letters.
The first letters of 'considered you' is 'cy'.
'i'+'cy'='ICY'
(Other definitions for icy that I've seen before include "Glacial" , "Distant - freezing" , "frozen over!" , "Frosty and slippy" , "Freezing and slippy" .)