Make contact when you reach the bottom (5,4)

I believe the answer is:

touch base

I'm a little stuck... Click here to teach me more about this clue!

'make contact' is the definition.
(synonyms)

'reach the bottom' is the wordplay.
'reach' becomes 'touch' (synonyms).
'the bottom' becomes 'base' (base is a kind of bottom).
'touch'+'base'='TOUCH BASE'

'when you' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for touch base that I've seen before include "Report back briefly" , "get in contact!" .)

I've seen this clue in The Irish Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.