---

All answers having "Pay attention!" as clue:

3 Character Answers:

---

HEY



4 Character Answers:

---

AHEM

HARK

HEAR

HEED

LOOK

MIND

NOTE

TEND



5 Character Answers:

---

FOCUS

SITUP



6 Character Answers:

---

LISTEN

TUNEIN

WAKEUP



7 Character Answers:

---

HEARKEN

SEEHERE



8 Character Answers:

---

LISTENUP

LOOKATME

TAKEHEED

TAKENOTE



9 Character Answers:

---

LENDANEAR

LOOKALIVE

WATCHTHIS



10 Character Answers:

---

LISTENHERE

TAKENOTICE



15 Character Answers:

---

GETTHISSTRAIGHT