Musician from Portugal appearing in seaside venue (5)
I believe the answer is:
piper
'musician' is the definition.
(piper is a kind of musician)
'portugal appearing in seaside venue' is the wordplay.
'portugal' becomes 'p'.
'appearing in' indicates putting letters inside.
'seaside venue' becomes 'pier'.
'p' placed into 'pier' is 'PIPER'.
'from' acts as a link.
(Other definitions for piper that I've seen before include "Military musician" , "Highland musician" , "eg Flautist" , "Scots musician" , "If you pay him, call the tune" .)