Natural tendency is to admit nothing initially before time in court (8)
I believe the answer is:
instinct
'natural tendency' is the definition.
(I've seen this before)
'is to admit nothing initially before time in court' is the wordplay.
'to admit' means one lot of letters goes inside another.
'initially' indicates taking the first letters.
'before' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'court' becomes 'ct' (abbreviation used in road names).
The first letter of 'nothing' is 'n'.
'is' going around 'n' is 'ins'.
'ins'+'t'+'in'+'ct'='INSTINCT'
(Other definitions for instinct that I've seen before include "Intuition, sixth sense" , "Inborn pattern of behaviour" , "Nothing learned" , "Innate behavioural pattern" , "Innate feeling" .)