Maybe crawl further than known male around Whitehall area? (7)
I believe the answer is:
outswim
'maybe crawl further than' is the definition.
(crawl is a style of swimming)
'known male around whitehall area?' is the wordplay.
'known' becomes 'out' (I've seen this before).
'male' becomes 'm' (common abbreviation).
'around' means one lot of letters goes inside another.
'whitehall area?' becomes 'swi' (SW1, postcode of Whitehall in London).
'out'+'m'='outm'
'outm' enclosing 'swi' is 'OUTSWIM'.
(Other definitions for outswim that I've seen before include "best in gala" , "Go faster or further through the water" .)