Sentimentality of team’s leader with small head (8)

'sentimentality' is the definition.
(twee can mean sentimental or quaint)

'team's leader with small head' is the wordplay.
'leader' says to take the initial letters.
'with' is a charade indicator (letters next to each other).
'small' becomes 'wee' (Scottish term for small).
'head' becomes 'ness' (ness is a headland).
The first letter of 'teams' is 't'.
't'+'wee'+'ness'='TWEENESS'

'of' acts as a link.