Secure the services of border's retail chain (6)

I believe the answer is:

retain

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'secure the services of' is the definition.
(I've seen this in another clue)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for retain that I've seen before include "Not relinquish" , "Hold in position" , "Keep, hold on to something" , "Keep in Tirane" , "Keep in place" .)

I've seen this clue in The Irish Times.

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