Helping call centre is sensible (8)
I believe the answer is:
rational
'sensible' is the definition.
(associated in meaning)
'helping call centre' is the wordplay.
'helping' becomes 'ration' (a ration is a serving or helping).
'centre' indicates the central letters.
The centre of 'call' is 'al'.
'ration'+'al'='RATIONAL'
'is' acts as a link.
(Other definitions for rational that I've seen before include "Based on logic or reasoning" , "Using logic" , "Sane; able to think" , "Able to reason" , "Based on reason or logic" .)