sysuse auto
quietly reg price length foreign#c.gear_ratio
est store test
esttab *, drop(*foreign*)

. esttab *, drop(*foreign*)

----------------------------
                      (1)
                    price
----------------------------
length              66.43***
                   (3.80)

_cons              1299.3
                   (0.24)
----------------------------
N                      74
----------------------------
t statistics in parentheses
* p<0.05, ** p<0.01, *** p<0.001

. esttab *, drop(*foreign*)

----------------------------
                      (1)
                    price
----------------------------
length              66.43***
                   (3.80)
mean(foreign#c.gear_ratio) WHATEVER

_cons              1299.3
                   (0.24)
----------------------------
N                      74
----------------------------
t statistics in parentheses
* p<0.05, ** p<0.01, *** p<0.001