Related Clues:

• Grouse quietly
• It can be acoustic or electric
• Sister Rosetta Tharpe's instrument
• Fender instrument
• 'Teardrops on My ___' (Taylor Swift song)
• Grumble has come from middle of stomach, say
• Gripe under one's breath
• Maiden to speak, speak indistinctly
• Fool here essentially gets to speak in a barely audible voice
• Grub in tea urn, oddly, and a musical instrument!