The answers to the clues below will have two things in common.

1. Sewer substitute 

2. Gathering after hitting the slopes

3. Monkey bars

4. Small, mass-produced toys and trinkets

Answers:

 

1. Septic tank

2. Apres ski

3. Jungle gym

4. Novelties - - - Answers begin with abbreviations of the four 30-day months:

1. SEPTic tank

2. APRe ski

3. JUNgle gym

4. NOVelties