Overbearing tail coat lined with titanium (8)
I believe the answer is:
dogmatic
'overbearing' is the definition.
(thesaurus)
'tail coat lined with titanium' is the wordplay.
'tail' becomes 'dog' (both can mean to follow).
'coat' becomes 'mac' (mac is a kind of coat).
'lined with' means one lot of letters goes inside another (as in being filled or lined with something).
'titanium' becomes 'Ti' (Ti is the chemical symbol for titanium).
'mac' placed around 'ti' is 'matic'.
'dog'+'matic'='DOGMATIC'
(Other definitions for dogmatic that I've seen before include "Stating opinions forcefully and arrogantly" , "Opinionated" , "Asserting positively" , "Giving opinions in arrogant know-all way" , "Stating opinions as if unquestionable" .)