Delay sweetheart acquiring tattoos for relationship (7)
I believe the answer is:
linkage
'for relationship' is the definition.
(thesaurus)
'delay sweetheart acquiring tattoos' is the wordplay.
'delay' becomes 'lag' (lag is a kind of delay).
'sweetheart' becomes 'e' (the heart/centre of 'sweet').
'acquiring' is an insertion indicator.
'tattoos' becomes 'ink' (I've seen this in another clue).
'lag'+'e'='lage'
'lage' placed around 'ink' is 'LINKAGE'.
(Other definitions for linkage that I've seen before include "Leaking (anag)" , "Connection, bond" , "Connection, coupling" , "Part of mechanism" , "System of connections" .)