Correct

插足

/ chāzú / 
Strokes

Definition

to squeeze in/to step in/to take part/to step between (two persons in a relationship)

Example

As a Verb

have a foothold in; set foot in; put one's foot in

1
Dàolù
道路
yòu
又
zāng
脏
yòu
又
nínìng
泥泞
  
,
méiyǒu
没有
chāzú
插足
de
的
dìfāng
地方
  
。

The road is dirty and muddy. It's hard to set foot in it.

As a Verb

participate/partake in; take part in; get involved in

2
Zài
在
zhīdào
知道
zhēnshí
真实
qíngkuàng
情况
zhīqián
之前
  
,
nǐ
你
bù
不
yìng
应
chāzú
插足
cǐshì
此事
  
。

Before knowing the truth, you shouldn't get involved in it.

3
Yóuyú
由于
dìsānzhě
第三者
chāzú
插足
  
,
líhūnlǜ
离婚率
zhúnián
逐年
shàngshēng
上升
  
。

The divorce rate is going up year by year as a result of marital infidelity.