Dt Crossword 27,079

[nicholas4300]

Hello All CrosswordLanders. I am struggling with the final solution to Saturday's "Daily Telegraph" Crossword 27,079. 23 across. 7 letters.
R?T?I?S Clue "Keeps checks restricting irregular soldiers" It must be
"Retains" But why so? Any assistance will be appreciated. Thanks in advance.

[glasman]

Reins + TA (Territorial Army)

[Lie-in King]

Yes, 'Retains' (keeps) - 'TA' (Territorial Army, in) 'reins' (checks)

[JoolsTwo]

Checks = Reins Inside it Ta for regular army.

[nicholas4300]

Thanks Glasman, why is it so obvious once you know?!

[glasman]

The penny takes a very long time to drop for me sometimes as well.

[nicholas4300]

Thanks to you Lie-in King and JimJools as well. Why I could not see that I do not know. I think I need to have a word with myself!