Check pressure again (8)
I believe the answer is:
restrain
'check pressure again' is the definition.
I can't tell whether this definition defines the answer.
'check pressure' is the wordplay.
'check' becomes 're' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pressure' becomes 'strain' (I've seen this before).
're'+'strain'='RESTRAIN'
(Other definitions for restrain that I've seen before include "Hold back, tether" , "bar" , "bottle up" , "stay" , "Arrest - confine - subdue" .)