Harbours weak heart, but takes part in games (8)

'harbours' is the definition.
('seaport' can be a synonym of 'harbour')

'weak heart but takes part in games' is the wordplay.
'weak' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'heart' means to look at the middle letters.
'but' becomes 'bar' (both can mean 'excluding' or 'except').
'takes part in' means one lot of letters goes inside another.
'games' becomes 'sports' (I've seen this before).
The centre of 'bar' is 'a'.
'e'+'a'='ea'
'ea' put into 'sports' is 'SEAPORTS'.

Can you help me to learn more?