Keep check, receiving thanks (6)
I believe the answer is:
retain
'keep' is the definition.
(retaining is a kind of keeping)
'check receiving thanks' is the wordplay.
'check' becomes 'rein' (both can mean to control or limit).
'receiving' indicates putting letters inside.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'rein' placed around 'ta' is 'RETAIN'.
(Other definitions for retain that I've seen before include "Keep; remember" , "Keep in Tirane" , "Continue to hold on to" , "Hold onto" , "Hire - keep" .)