First in, I turned tail (7)
I believe the answer is:
initial
'first' is the definition.
('initial' can be similar in meaning to 'first')
'in i turned tail' is the wordplay.
'turned' is an anagram indicator.
'tail' is an anagram of 'tial'.
'in'+'i'+'tial'='INITIAL'
(Other definitions for initial that I've seen before include "First letter of a name" , "Occurring at the start" , "subscribe, minimally" , "Start of name" , "Primary" .)