Related Clues:

• Channel crosser Gertrude
• Arched body part
• Olympic swimmer Gertrude
• English Channel swimmer of '26
• Sandal, mainly
• Swimmer who channeled her energy?
• A lone flat fish?
• Exclusive class of fish
• A lone fish?
• The fish is alone
• Exclusive, only
• Kind of fish - lose it
• A lone sort of fish - lose it
• A lonely sort of flatfish
• You've only got to see 36 across for this.