Second pensioner in Bath bar? (4)
I believe the answer is:
soap
'bath bar?' is the definition.
(I've seen this in another clue)
'second pensioner' is the wordplay.
'second' becomes 's' (common abbreviation).
'pensioner' becomes 'OAP' (old age pensioner).
's'+'oap'='SOAP'
'in' acts as a link.
(Other definitions for soap that I've seen before include "made in a bar?" , "Washing aid" , "Cleansing bar" , "Washing substance" , "Cleansing substance" .)