Possible Clues:

• Has some gall putting fruit behind tree
• Outer door for pupil with gall
• Gall of Robin aka Ruthven or in people being cut out
• Gall present in two trees
• Gall from retiree detaining a knight with short appeal
• Gall evident, as a Greek character cut short in Spanish expression
• Spongy tree gall
• Gall wasp's lump
• Gall caused by insects on a tree
• Not the sort that had the gall to cause trouble in Eden