One uniform with a tiny variation (5)
I believe the answer is:
unity
'one' is the definition.
(synonyms)
'uniform with a tiny variation' is the wordplay.
'uniform' becomes 'U' (phonetic alphabet: alpha, bravo, charlie etc.).
'with' means one lot of letters go next to another.
'variation' is an anagram indicator.
'tiny' is an anagram of 'nity'.
'u'+'nity'='UNITY'
(Other definitions for unity that I've seen before include "Concord" , "Completeness (with nothing wanting)" , "Number one" , "Oneness, harmony" , "A single whole" .)