Pay heed (6)
I believe the answer is:
attend
'pay heed' is the definition.
(I know that pay heed can be written as attend)
This is all the clue.
(Other definitions for attend that I've seen before include "Be there ? pay attention" , "Being 16 [LISTEN]" , "Be present at, turn up" , "Completed" , "take heed" .)