Keep your thanks in check (6)
I believe the answer is:
retain
'keep' is the definition.
(I know that keep can be written as retain)
'thanks in check' is the wordplay.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'in' is an insertion indicator.
'check' becomes 'rein' (both can mean to control or limit).
'ta' inserted into 'rein' is 'RETAIN'.
'your' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for retain that I've seen before include "Save" , "Keep in Tirane" , "Hold onto" , "Continue to hold on to" , "Keep; remember" .)