Smart medico got messy without leadership (6)
I believe the answer is:
dressy
'smart' is the definition.
(I've seen this before)
'medico got messy without leadership' is the wordplay.
'medico' becomes 'Dr' (synonyms).
'got' means one lot of letters go next to another.
'without leadership' means to remove the first letter.
'messy' with its initial letter removed is 'essy'.
'dr'+'essy'='DRESSY'
(Other definitions for dressy that I've seen before include "Stylishly attired" , "Nattily attired, wearing stylish clothes" , "Smartly clothed" , "(Of clothes) smart, formal" , "Wearing stylish clothing" .)