Possible Clues:

• One might, to be sure, claim that this was the insect of 3 down
• Definite and unyielding
• He was born Stuart Goddard
• Can you be positive that the fatherly fellow is in at this?
• Legendary rock singer of the 1980s
• Resolute, a worker crossing barrier
• Positively the first insect
• Obstinate
• Insisting
• Impossible to move