Self-confidence of model entertaining one (5)
I believe the answer is:
poise
'self-confidence' is the definition.
(I've seen this before)
'model entertaining one' is the wordplay.
'model' becomes 'pose' (synonyms).
'entertaining' means one lot of letters goes inside another.
'one' becomes 'i' (roman numeral).
'pose' going around 'i' is 'POISE'.
'of' acts as a link.
(Other definitions for poise that I've seen before include "Grace; equilibrium" , "Self-confidence" , "Dignified and self-assured manner" , "Coolness and composure under strain" , "Balance; composure" .)