Bit of training by hospital to take pulse (5)
I believe the answer is:
throb
'pulse' is the definition.
(throb is a kind of pulse)
'bit of training by hospital to take' is the wordplay.
'bit of' suggests taking the first letters.
'by' means one lot of letters go next to another.
'hospital' becomes 'h'.
'to take' becomes 'rob'.
The first letter of 'training' is 't'.
't'+'h'+'rob'='THROB'
(Other definitions for throb that I've seen before include "Beat strongly" , "Drum" , "beat repeatedly" , "Strong rhythmic beat" , "Pulsate with force" .)