Sailor and worker initially upsetting the French spider (9)
I believe the answer is:
tarantula
'spider' is the definition.
(I know that tarantula is a type of spider)
'sailor and worker initially upsetting the french' is the wordplay.
'sailor' becomes 'tar' (tar can mean a sailor).
'and' means one lot of letters go next to another.
'worker' becomes 'ant' (worker is a type of ant).
'initially' says to take the initial letters.
'the french' becomes 'la' ('the' in French).
The first letter of 'upsetting' is 'u'.
'tar'+'ant'+'u'+'la'='TARANTULA'
(Other definitions for tarantula that I've seen before include "Leggy creature" , "web architect" , "small, venomous creature" , "Hairy arachnid" , "Breed of spider" .)