Tuna scarce? Perhaps - and lobster, for example (10)
I believe the answer is:
'lobster for example' is the definition.
(lobster is a kind of crustacean)
'tuna scarce? perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'tunascarce' with letters rearranged gives 'CRUSTACEAN'.
'and' is the link.
(Other definitions for crustacean that I've seen before include "Animal like a crab" , "crab maybe" , "crab, for example?" , "Perhaps crab" , "Hard-shelled arthropod" .)