Clue: Partner of 1 in row that's overheard (5)
Answer: SKULL
Explanation: Partner of 1 in row that's overheard (5)

Homophone [*that's overheard*] of **SCULL** ("row")
 

 
*The 1 referred to is CROSSBONES (1 ac) – i.e. SKULL and CROSSBONES (as seen on the Jolly Roger)